J. Anim. Sci. 2005. 83:816-824
© 2005 American Society of Animal Science
ANIMAL GROWTH, PHYSIOLOGY, AND REPRODUCTION |
Effects of recombinant bovine somatotropin on growth and abundance of mRNA for IGF-I and IGF-II in channel catfish (Ictalurus punctatus)1,2
B. C. Peterson3,
G. C. Waldbieser and
L. Bilodeau
ARS, USDA Catfish Genetics Research Unit, Thad Cochran National Warmwater Aquaculture Center, Stoneville, MS 38776
 |
Abstract
|
|---|
Research was conducted to examine growth rates, circulating concentrations of IGF-I, and mRNA abundance levels of IGF-I and IGF-II in channel catfish (Ictalurus punctatus) given recombinant bovine ST (rbST; Posilac, Monsanto Co., St. Louis MO). In the first study, juvenile catfish (5.5 ± 0.5 g) were randomly assigned to one of three treatments: 1) sham-injected control (one needle puncture per week); 2) rbST (30 µg•g BW–1•wk–1; Posilac); and 3) nonhandled control (control). At the end of the 6-wk study, the fish were weighed, measured for length, and G:F was determined. Compared with sham and control treatments, rbST-treated fish had 48% greater final BW, 14% greater total length, and 52% greater G:F (P < 0.001). In the second study, juvenile catfish (41.1 ± 1.5 g) were assigned randomly to one of two treatments: 1) sham or 2) rbST. Eight fish per treatment were sampled on d 0, 1, 2, 7, 14, and 21 for blood, muscle, and liver. Relative expression of IGF-I and IGF-II mRNA was determined by real-time PCR and plasma concentrations of IGF-I were measured using a validated fluoroimmunoassay. Circulating concentrations of IGF-I were increased (37.9 ± 5.5 vs. 22.0 ± 6.6 ng/mL; P < 0.05) in rbST-injected fish compared with sham-injected controls by d 14. Liver IGF-I and IGF-II mRNA was increased 4.3-and 14.4-fold, respectively, by d 1 in rbST-injected fish compared with controls (P < 0.05); however, abundance of liver IGF-I and IGF-II mRNA did not differ from controls on d 0, 2, 7, 14, and 21. Abundance of muscle IGF-I and IGF-II mRNA did not differ in rbST-injected fish compared with controls throughout the study. Results of the first study demonstrated that rbST improves growth performance of channel catfish. Results of the second study showed that the growth-promoting effects of rbST were not mediated by the expression of IGF-I or IGF-II mRNA in the muscle. Instead, the results suggest that rbST promotes growth by stimulating plasma IGF-I release, possibly through its direct effect on the liver or on local tissues to synthesize IGF-I. The changes in mRNA abundance and plasma concentrations of IGF-I support the role of IGF-I in growth regulation of channel catfish.
Key Words: Catfish • Insulin-Like Growth Factor-I • Insulin-Like Growth Factor-II • Somatotropin
|
Introduction
|
|---|
Within the last 30 yr, the growth-promoting effects of somatotropin have been well documented in a variety of fish species (reviewed by McLean and Donaldson, 1993
), including channel catfish (Ictalurus punctatus; Wilson et al., 1988; Silverstein et al., 2000; Peterson et al., 2004a). An increase in commercial production of channel catfish has created interest regarding the use of recombinant bovine ST (rbST) to increase yields in aquaculture. To date, use of rbST in aquaculture has been impeded by a lack of practical and economically feasible methods of administration as well as negative public perception of hormone-treated products (Heitzman et al., 1981). Until technologies advance that allow rbST to be administered economically and/or public perception changes, its use in aquaculture will be limited to small-scale research studies. Its use in research will provide a better understanding of genes and gene products that are involved in growth regulation.
The ST-IGF network plays a major role in the endocrine control of fish growth (Peter and Marchant, 1995; Le Bail et al., 1998; Moriyama et al., 2000). The role of the ST-IGF network in channel catfish, the major aquaculture species in the southeastern United States, is unclear and only one catfish study has suggested a role for IGF-I in growth (Silverstein et al., 2000). With the importance of ST and the IGF in growth regulation in other fish species (Kajimura et al., 2001; Biga et al., 2004), the objectives of the present research were to examine the effects of rbST on growth performance as well as to better understand the roles of IGF-I and IGF-II in growth regulation of channel catfish.
|
Materials and Methods
|
|---|
Treatments
The channel catfish used in this study were from the USDA103 strain that originated from broodstock maintained at the USDA-ARS Catfish Genetics Research Unit, Stoneville, MS, aquaculture facility. In the first study, 90 fish (5.5 ± 0.5 g; three tanks per treatment) were randomly assigned to nine 76-L tanks (10 fish per tank), and allowed to acclimate for 7 d. The treatments were as follows: 1) sham-injected control (one needle puncture per week); 2) rbST (30 µg•g BW–1•wk–1; Posilac, Monsanto Co., St. Louis, MO); and 3) nonhandled control (control). Fish were injected with a 30-gauge, 0.5-mL insulin syringe (BD Ultra-Fine II, Becton, Dickinson and Co., Franklin Lakes, NJ). Sham-and rbST-treated fish were weighed as a group (tank) and received a weekly i.p. injection, just anterior to the pelvic fin. Controls were weighed as a group (tank) on d 0 and 42 of the study. All fish were fed once per day to apparent satiation and reared in 26.0°C flow-through well water and a 14-h light:10-h dark photoperiod. Apparent satiation was obtained by feeding each tank of fish as much as they would eat during a 10-min period. Small amounts of feed were added to each tank to ensure minimal waste. Uneaten food was collected and weighed back, whereas small amounts of food were unaccounted for. A commercial 36% CP (DM basis) floating catfish feed (Farmland Industries, Inc., Kansas City, MO) was used throughout the study. Water quality (i.e., pH approximately 8.5 and dissolved oxygen levels >5.0 mg/L) and flow rates (7.6 L/min) were similar among tanks. The amount of feed consumed by fish in each tank was recorded at the end of the study. Fish in all tanks were killed with an overdose (300 ppm) of tricaine methanesulfonate (Argent Chemical Laboratories, Redmond, WA) on d 42. Fish were weighed as a group (10 fish per tank), and individual fish lengths were recorded.
In the second study, 96 fish (12 per tank) weighing 41.1 ± 1.5 g were randomly assigned to one of two treatments with four replicate aquaria per treatment. The treatments were as follows: 1) sham or 2) rbST (30 µg•g BW–1•wk–1). The fish were acclimated and maintained as described above. The fish used in the second study were larger to ensure that a sufficient quantity of plasma would be collected for the IGF-I assay. Beginning on d 0, sampled fish were killed, bled from the caudal vasculature, and muscle and liver samples were excised.
Both studies were conducted in accordance with the principles and procedures approved by the Institutional Animal Care and Use Committee, USDA-ARS Catfish Genetics Research Unit.
Sample Preparation and RNA Isolation
A transverse slice of white epaxial muscle (approximately 100 mg) located beneath the dorsal fin and a section of liver (approximately 100 mg) were taken for RNA extraction. Samples were immediately placed in 1 mL of TRIzol (Life Technologies, Rockville, MD), flash-frozen in liquid N, and stored at –80°C. Total RNA was isolated according to the manufacturer’s recommendations and used for analysis of IGF-I and IGF-II mRNA from muscle and liver tissues. On sampling days (0, 1, 2, 7, 14, and 21) in the second study, eight fish per treatment (two fish per tank) were killed and sampled as described above. The integrity of the RNA preparations was verified by visualization of the 18S and 28S ribosomal bands stained with ethidium bromide after electrophoresis on 2.0% agarose gels. Total RNA was quantified by measuring the absorbance at 260 nm with a NanoDrop ND-100 spectrophotometer (NanoDrop Technologies, Rockland, DE).
Real-Time Polymerase Chain Reaction
Ribonucleic acid (1 µg) from liver and muscle was reverse-transcribed in 10-µL reactions using the iScript cDNA synthesis kit (BioRad, Hercules, CA). Real-time PCR was performed using the iCycler iQ (BioRad). The primers, probes, and accession numbers for IGF-I, IGF-II, and 
-tubulin are listed in Table 1. Primer and probe sequences were designed with Beacon Designer 2.0 (Premier BioSoft Int., Palo Alto, CA) software. Each amplification reaction mixture (12.5 µL) contained 300 ng of cDNA; 1x iQ Supermix (Bio-Rad), which comprised 10 mM KCl, 4 mM Tris•HCl, pH 8.4, 0.16 mM deoxyribo-nucleotide triphosphate, 5 U/mL iTaq polymerase, 0.6 mM MgCl2, and stabilizers; 10 µM (IGF-I, IGF-II, or alpha tubulin) of each primer; and a dual-labeled probe (5 µM of IGF-I or IGF-II; 1 µM of -tubulin). The real-time PCR protocol for IGF-I, IGF-II, and -tubulin was 3 min at 95°C; 45 cycles of 95°C for 15 s; and 60°C for 1 min.
View this table:
[in this window]
[in a new window]
|
Table 1. Nucleotide sequences of the PCR primers and probes used to assay gene abundance by real-time quantitative PCR
|
|
Real-time PCR results were analyzed by subtracting the mean of the -tubulin (reference sequence) thresh- old cycle (CT) values from the mean of the IGF-I or IGF- II (target sequences) CT values for both the treated (rbST) and the control (Sham) samples to obtain 
CT values (Johnson et al., 2000). The CT values of the control samples were then subtracted from the CT values of the treated samples to obtain the CT values. The fold induction in levels of IGF-I or IGF-II in rbST-treated samples compared with the control samples was obtained by the formula 2– CT (Johnson et al., 2000). This method has been successfully applied to quantitative determination of abundance of mRNA for IGF-I and IGF-II in common carp (Cyprinus carpio) (Vong et al., 2003).
Validation of Target and Reference Amplification
The efficiency of the target amplification and the efficiency of the reference amplification must be similar for the CT calculation to be valid. To assess whether IGF-I, IGF-II, and -tubulin had similar amplification efficiencies, we examined how changes in relative CT values (CT) varied with template dilution (Vong et al., 2003). The CT values for IGF-I and IGF-II were plotted against the logarithm of the dilution factor of template cDNA, and the slopes were determined.
Insulin-Like Growth Factor-I Fluoroimmunoassay
Plasma IGF-I concentrations were measured using a competitive time-resolved fluoroimmunoassay validated for channel catfish (Small and Peterson, 2005). Recombinant barramundi (fish) IGF-I standard and anti-barramundi IGF-I polycolonal antibody were purchased commercially (GroPep Pty. Ltd., Adelaide, S.A., Australia). PerkinElmer Life Sciences (Norton, OH) prepared the europium-labeled IGF-I tracer via N-terminal labeling of recombinant barramundi (fish) IGF-I with dissociation enhanced lanthanide fluorescence immunoassay Eu-N1 Isothiocyanate (ITC) lanthanide chelate (Reference 1244–302, PerkinElmer). Sensitivity of the assay was 0.20 ng/mL, and intra- and interassay CV were <7 and <12%, respectively. Serial dilution of plasma was parallel to the standard curve and recovery of IGF-I from spiked plasma samples was >90%. Plasma samples were acid-ethanol–extracted prior to assaying (Breier et al., 1990) and standards were run in triplicate, whereas samples were run in duplicate.
Statistical Analyses
In the first study, data were analyzed by ANOVA with SAS v. 9.0 software (SAS Inst., Inc., Cary, NC), with tank serving as the experimental unit. The model included the effects of treatment on BW, length, intake, and G:F. Least squares means were generated and separated using the PDIFF option of SAS for main effects. A significance level of P <0.05 was used. In the second study, data were analyzed by using the GLM procedures of SAS for a repeated measures design. The model included the main effect of time (0, 1, 2, 7, 14, and 21 d) and time x treatment interaction. When the main effect was significant (P < 0.05), least squares means separation was accomplished by the PDIFF option of SAS.
|
Results and Discussion
|
|---|
Validation of Real-Time PCR Assay
Primer and probe concentrations were optimized using liver cDNA as template. Figure 1 shows that the relationship between the CT value and the logarithm of the dilution factor of cDNA template for the target genes IGF-I and IGF-II was 0.98 and 0.99, whereras for -tubulin, it was 0.99. The slope of the CT vs. log dilution factor plot for IGF-I/-tubulin was 0.090 and the slope of the CT vs. log dilution factor plot for IGF-II/-tubulin was 0.070, less than the recommended value of 0.1 (Johnson et al., 2000; Figure 2). Therefore, conditions for amplifying IGF-I/-tubulin and IGF-II/-tubulin were reliable in adopting the comparative CT method.
View larger version (14K):
[in this window]
[in a new window]
|
Figure 1. Relationship between CT values and the logarithm of the dilution factor of liver cDNA. The graphs were generated using A) IGF-I specific primers and probe, B) IGF-II specific primers and probe, and C) -tubulin specific primers and probe. The CT values represent pooled cDNA from five fish sampled on d 0.
|
|
Experiment 1
Final fish BW of the sham and control did not differ and were therefore combined. Final BW was increased (P < 0.001) 48% (25.6 ± 0.5 g) in the rbST-treated fish compared with the average final BW of the sham and control (17.2 ± 0.6 g; Table 2). We have previously reported gains in Norris (16%) and USDA103 (27%) strains of channel catfish administered rbST every 3 wk for 9 wk (Peterson et al., 2004a). In the previous research, rbST was injected at doses of 30, 60, and 120 µg/g BW, and results indicated that more frequent injections of rbST would be required to observe an optimal growth response. A significant difference in BW gain between the rbST-treated fish and sham was observed at d 21, 28, 35, and 42 (Figure 3). This is in contrast to our previous study, in which a difference in BW gain was not observed until the last 3 wk of the study (Peterson et al., 2004a). Other research investigating the use of rbST in channel catfish has used lyophilized rbST reconstituted in glycine buffer or saline. Catfish administered rbST at a dose of 10 µg/g BW every week were 44.8% heavier than controls (Wilson et al., 1988). Norris and USDA103 catfish injected with rbST at a dose of 2.5 µg/g BW every week also demonstrated increased growth (Silverstein et al., 2000).
View larger version (12K):
[in this window]
[in a new window]
|
Figure 3. Body weight gain of channel catfish over 42 d. Treatments were recombinant bovine somatotropin (rbST; 30 µg•g BW–1•wk–1; Posilac, Monsanto Co., St. Louis, MO); sham-injected control (one needle puncture per week; and nonhandled control (control). Sham- and rbST-treated fish were injected i.p. on d 0 and once weekly for 42 d. Each point shows the average BW of individual fish in each treatment (mean ± SEM) calculated from three replicate tanks. Asterisks indicate a difference (P < 0.05) between sham or nonhandled controls and rbST-injected fish.
|
|
Water temperature rbST was shown to prolong the release of exogenous rbST in rainbow trout at 15°C (Garber et al., 1995), Coho and Chinook salmon at 10.3°C (McLean et al., 1997), and tilapia at 29°C (Leedom et al., 2002). Clearance rates for exogenous rbST differed in these studies but were probably related to the viscosity of the Posilac formulation at different temperatures. Posilac is more viscous at lower temperatures, which would extend the duration over which rbST is released (Leedom et al., 2002). Although the optimal dose and frequency of administration of rbST in catfish is not known, the results of present and previous research suggest that rbST must be administered at least weekly or at a larger dose to realize full growth enhancement in channel catfish.
Increases in length have previously been reported in catfish administered rbST (Peterson et al., 2004a). These results agree with previous research, in which an increase in length also has been observed in rainbow trout administered rbST (Garber et al., 1995) or ovine ST (Foster et al., 1991).
Treatment with rbST increased (P < 0.001) average total length by approximately 14% and improved average G:F by 52% (Table 2
). The effects of rbST on feed efficiency are not clear. Using fingerling channel catfish (approximately 9 g), Wilson et al. (1988) demonstrated that rbST improved feed efficiency only for the first 4 wk of the study. Silverstein et al. (2000) observed that rbST improved feed efficiency in catfish maintained at 21.7°C, but not at 26.0°C, whereas Peterson et al. (2004a) found that the only significant improvement in feed efficiency was during the last 3 wk of the 9-wk study. Improved feed efficiency has been reported in other fish species (Markert et al., 1977; Agellon et al., 1988, Garber et al., 1995) treated with ST. Gain-to-feed ratios were lower in controls and rbST-treated fish in the current study compared with our previous work (Peterson et al., 2004a). Reasons for the poorer feed efficiency are unclear, but it may be related to feed wastage. Each day, uneaten food was collected from each tank and weighed back, but it is possible that a small amount of food went down the standpipe. Feed that was not accounted for would explain the lower G:F.
Feed intake was not different between the two controls (sham and control) and rbST-treated fish (Table 2), which is similar to our previous research (Peterson et al., 2004a). However, there was a 16 and 69% increase in feed consumption, respectively, in rbST-injected catfish in the studies of Silverstein et al. (2000) and Wilson et al. (1988). Previously reported effects of ST treatment on feed intake in other species of fish have been variable. Agellon et al. (1988) reported that rainbow trout treated with recombinant salmon ST consumed more feed and consumed it more aggressively compared with untreated fish. In contrast, Garber et al. (1995) reported a decrease in feed intake within the first 14 d in rainbow trout treated with rbST, but intake was not different throughout the duration of the experiment. Similarly, Markert et al. (1977) observed no treatment effect of rbST on feed intake of Coho salmon. The doses of ST used in the above mentioned studies were not the same and this may have also contributed to differences in intake. Feed intake may be influenced by a variety of factors such as salinity (Kayes, 1977), temperature (Brett et al., 1969), species body and viscera size (Paloheimo and Dickie, 1966), and rate of digestion (Windell, 1967). Thus, the effect of rbST on feed intake in channel catfish is still unclear.
Experiment 2
Many fish species demonstrate ST regulation of IGF-I mRNA. For example, injection of ST has been shown to significantly increase the IGF-I mRNA levels in the liver of Coho salmon (Cao et al., 1989), rainbow trout (Biga et al., 2004), and sea bream (Duguay et al., 1996). The ST-induced increase in IGF-I mRNA abundance is typically accompanied by an increase in circulating concentrations of IGF-I (Biga et al., 2004). In our study, liver IGF-I mRNA abundance was increased approximately fourfold by d 1 in rbST-injected fish compared with controls (P < 0.05; Figure 4A); however, abundance of liver IGF-I mRNA was not different from controls on any of the other days that fish were sampled. In addition, abundance of muscle IGF-I mRNA was not different in rbST-injected fish compared with controls throughout the 21-d study (Figure 4B). In contrast, liver and muscle IGF-I mRNA levels were elevated in rbST-treated rainbow trout throughout a 28-d study (Biga et al., 2004). The difference in response of IGF-I mRNA abundance in the liver and muscle in our study and the study with rainbow trout could be explained by the faster clearance rates of rbST. Posilac is more viscous at lower temperatures, which would extend the duration over which rbST is released in trout. The transient effect of rbST on abundance of muscle and liver IGF-I mRNA observed in our study may have been due to a possibly faster clearance rate of exogenous rbST in the warmer water. Perhaps larger differences in muscle and liver IGF-I mRNA abundance would have been observed with a greater dose of rbST or a more frequent injection regimen. It is also possible that IGF-I may have an important autocrine/paracrine role in catfish. Perhaps treatment with rbST increased IGF-I mRNA abundance at local tissue sites as well as through the liver (Sjogren et al., 1999). Previous studies with mice that have had the IGF-I gene deleted in the liver have shown that liver IGF-I is not essential for normal growth and development (Sjogren et al., 1999; Yakar et al., 1999). It is also possible that IGF-I mRNA is being transcribed at a maximal rate in these fast growing juvenile catfish (Peterson et al., 2004b). In a study comparing slow- and fast-growing families of catfish, Peterson et al. (2004b) found no difference in the abundance of liver IGF-I mRNA.
View larger version (17K):
[in this window]
[in a new window]
|
Figure 4. Liver and muscle IGF-I mRNA abundance in recombinant bovine ST (rbST)-injected (30 µg•g BW–1•wk–1; Posilac, Monsanto Co., St. Louis, MO) and sham-injected (one needle puncture per week) catfish. Sham-and rbST-injected fish were injected i.p. on d 0 and once weekly for 21 d. Results are expressed as fold inductions on d 0, 1, 2, 7, 14, and 21 compared with each sham group. Values are means ± SEM (n = 8) for each time point calculated from four replicate tanks. Asterisks indicate a difference (P < 0.05) between sham- and rbST-injected fish.
|
|
Circulating concentrations of IGF-I increased (37.9 ± 5.5 vs. 22.0 ± 6.6 ng/mL; P < 0.05) in rbST-injected fish compared with sham-injected controls by d 14 (Figure 5). Concentrations of IGF-I did not differ between treatments on any of the other days. Silverstein et al. (2000) injected channel catfish with rbST (lyophilized rbST diluted with saline) once per week and showed an increase of IGF-I at wk 4 of the study. Insulin-like growth factor-I was not measured at any other time points in the study. In the current study, it is not clear why IGF-I was not greater in rbST-treated fish on d 21, but this may be related to the small sample size at each time point. It is also possible that IGFBP are playing a role in regulating IGF-I clearance. The presence of IGFBP has been detected in channel catfish (Johnson et al., 2003; Peterson et al., 2004a). We have shown that an approximately 45-kDa IGFBP, similar in molecular weight to mammalian IGFBP-3, is unique, in that it is not affected by ST administration in channel catfish (Peterson et al., 2004a). Others have shown it is actually decreased in catfish administered ST (Johnson et al., 2003). Johnson et al. (2003) suggested that the reductions in IGFBP might work to increase the bioavailability of free IGF-I. Perhaps IGFBP in catfish play an important role in regulating IGF-I. The current study, as well as the study of Silverstein et al. (2000), demonstrates that an increase in concentrations of IGF-I is associated with increased BW in rbST-injected catfish, supporting the role of IGF-I in the growth of channel catfish.
View larger version (22K):
[in this window]
[in a new window]
|
Figure 5. Circulating plasma concentrations of IGF-I in recombinant bovine ST (rbST)- and sham-injected catfish. Treatments were recombinant bovine somatotropin (rbST) (30 µg•g BW–1•wk–1; Posilac, Monsanto Co., St. Louis MO) and sham-injected control (one needle puncture per week). Sham- and rbST-treated fish were injected i.p. on d 0 and once weekly for 21 d. Blood was sampled on d 0, 1, 2, 7, 14, and 21. Each time point represents eight fish per treatment and shows the average concentration of IGF-I in each treatment (mean ± SEM) calculated from four replicate tanks. Asterisks indicate a difference (P < 0.05) between sham- and rbST-injected fish.
|
|
Information on fish IGF-II expression and regulation is increasing. There are reports that IGF-II mRNA is present in multiple fish tissues (Duguay et al., 1996; Vong et al., 2003; Caelers et al., 2004). In general, data for IGF-II mRNA indicate that IGF-II has an important role, not only during embryonic development, but also during postnatal growth. In our study, liver IGF-II mRNA was increased 14.4-fold (P < 0.001) by d 1 in rbST-injected fish compared with sham-injected fish, but it remained similar to the controls throughout the rest of the study (Figure 6). In addition, the abundance of muscle IGF-II mRNA did not differ in rbST-injected fish compared with controls throughout the 21-d study (Figure 6).
View larger version (15K):
[in this window]
[in a new window]
|
Figure 6. Liver and muscle IGF-II mRNA abundance in recombinant bovine ST (rbST)-injected (30 µg•g BW–1 •wk–1; Posilac, Monsanto Co., St. Louis MO) and sham-injected (one needle puncture per week) catfish. Sham-and rbST-injected fish were injected i.p. on d 0 and once weekly for 21 d. Results are expressed as fold inductions on d 0, 1, 2, 7, 14, and 21 compared with each sham group. Values are means ± SEM (n = 8) for each time point calculated from four replicate tanks. Asterisks indicate a difference (P < 0.001) between sham- and rbST-injected fish.
|
|
Our IGF-II expression data are similar to other ST-treated fish studies. Juvenile common carp (Cyprinus carpio) injected with porcine ST demonstrated a 2.7-fold increase in liver IGF-II mRNA level and a 3.4-fold increase in muscle IGF-II mRNA level 6 h after injection (Vong et al., 2003). In rainbow trout, IGF-II mRNA level in the pyloric ceca was increased as much as fourfold by ST administration (Shamblott et al., 1995); however, sea bream (Sparus aurata) treated with ST did not increase tissue IGF-II mRNA levels (Duguay et al., 1996). These differences may reflect differences in species or differences in the preparation of ST used in the study.
Results of the first study demonstrated that rbST accelerates growth rate and improves G:F in channel catfish. The results also showed that at least one of the mechanisms by which rbST increases growth is through an increase in length. Results of the second study show that the growth-promoting effects of rbST were not mediated by altered expression of IGF-I or IGF-II in the muscle. Instead, these results indicate that rbST promotes growth by stimulating plasma IGF-I release, possibly through its direct effect on the liver or on local tissues to synthesize IGF-I. The changes in mRNA and protein levels of IGF-I support its role in growth regulation of channel catfish. The high abundance of IGF-II mRNA in the liver after treatment with rbST suggests a role for IGF-II in postnatal growth of channel catfish.
|
Footnotes
|
|---|
1 The authors thank the assistance of M. Loden of the USDA-ARS Catfish Genetics Research Unit for performing the real-time PCR assays. 
2 Mention of trade names or commercial products is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture.
3 Correspondence to: 141 Experiment Station Rd. (phone: 662-686-3589; fax: 662-686-3567; e-mail: bpeterson{at}ars.usda.gov).
Received for publication October 19, 2004.
Accepted for publication January 6, 2005.
|
Literature Cited
|
|---|
Agellon, L. B., C. J. Emery, J. M. Jones, S. L. Davies, A. D. Dingle, and T. T. Chen. 1988. Promotion of rapid growth of rainbow trout (Salmo gairdneri) by a recombinant fish growth hormone. Can. J. Fish. Aquat. Sci. 45:146–151.
Biga, P. R., G. T. Schelling, R. W. Hardy, K. D. Cain, K. Overturf, and T. L. Ott. 2004. The effects of recombinant bovine somatotropin (rbST) on tissue IGF-I, IGF-I receptor, and GH mRNA levels in rainbow trout, Oncorhynchus mykiss. Gen. Comp. Endocrinol. 135:324–333.[Medline]
Breier, B. H., B. W. Gallaher, and P. D. Gluckman. 1991. Radioimmunassay for insulin-like growth factor-I: Solutions to some potential problems and pitfall. J. Endocrinol. 128:347–357.[Abstract]
Brett, J. R., J. E. Shelbourn, and C. T. Shoop. 1969. Growth rate and body composition of fingerling sockeye salmon, Oncorhynchus nerka, in relation to temperature and ration size. J. Fish. Res. Board Can. 26:2363–2394.
Caelers, A. G. Berishvili, M. L. Meli, E. Eppler, and M. Reinecke. 2004. Establishment of a real-time RT-PCR for the determination of absolute amounts of IGF-I and IGF-II gene expression in liver and extrahepatic sites of the tilapia. Gen. Comp. Endocrinol. 137:196–204.[Medline]
Cao, Q. P., S. J. Duguay, E. M. Plisetskaya, D. F. Steiner, and S. J. Chan. 1989. Nucleotide sequence and growth hormone-regulated expression of salmon insulin-like growth factor I mRNA. Mol. Endocrinol. 3:2005–2010.[Abstract]
Duguay, S. J., J. Lai-Zhang, D. F. Steiner, B. Funkenstein, and S. J. Chan. 1996. Developmental and tissue-regulated expression of IGF-I and IGF-II mRNAs in S. aurata. J. Mol. Endocrinol. 16:123–132.[Abstract]
Foster, A.R., D. F. Houlihan, C. Gray, F. Medale, B. Fauconneau, S. J. Kaushik, and P. Y. Le Bail. 1991. The effects of ovine growth hormone on protein turnover in rainbow trout. Gen. Comp. Endocrinol. 82:111–120.[Medline]
Garber, M. M., K. G. DeYonge, J. C. Byatt, W. A. Lellis, D. C. Honeyfield, R. C. Bull, G. T. Schelling, and R. A. Roeder. 1995. Dose-response effects of recombinant bovine somatotropin (Posilac) on growth performance and body composition of two-year-old rainbow trout (Oncorhynchus mykiss). J. Anim. Sci. 73:3216–3222.[Abstract]
Heitzman, R. J., S. N. Dixon, and D. J. Horwood. 1981. The measurement of residues of anabolic agents in tissues of farm animals and meat. Anim. Prod. 32:359–363.
Johnson, J., J. Silverstein, W. R. Wolters, M. Shimizu, W. W. Dickhoff, and B. S. Shepherd. 2003. Disparate regulation of insulin-like growth factor-binding proteins in a primitive, ictalurid, teleost (Ictalurus punctatus). Gen. Comp. Endocrinol. 132:122–130.
Johnson, M. R., K. Wang, J. B. Smith, M. J. Heslin, and R. B. Diasio. 2000. Quantitation of dihydropyrimidine dehydrogenase expression by real-time reverse transcription polymerase chain reaction. Anal. Biochem. 278:175–184.[Medline]
Kajimura, S., K. Uchida, T. Yada, L. G. Riley, J. C. Byatt, R. J. Collier, K. Aida, T. Hirano, and E. G. Grau. 2001. Stimulation of insulin-like growth factor-I production by recombinant bovine growth hormone in Mozambique tilapia, Oreochromis mossambicus. Fish Physiol. Biochem. 25:221–230.
Kayes, T. 1977. Effects of hypophysectomy, beef growth hormone replacement therapy, pituitary autotransplantation and environmental salinity on growth in the black bullhead (Ictalurus melas). Gen. Comp. Endocrinol. 33:371–381.[Medline]
Le Bail, P.-Y., V. Gentil, O. Noel, J. M. Gornez, F. Carre, P. Le Goff, and C. Weil. 1998. Structure, function, and regulation of insulin like growth factors in fish. Ann. N.Y. Acad. Sci. 839:157–161.[Free Full Text]
Leedom, T. A., K. Uchida, T. Yada, N. H. Richman III, J. C. Byatt, R. J. Collier, T. Hirano, and E. G. Grau. 2002. Recombinant bovine growth hormone treatment of tilapia: Growth response, metabolic clearance, receptor binding and immunoglobulin production. Aquaculture 207:359–380.
Markert, J. R., D. A. Higgs, H. M. Dye, and D.W. MacQuarrie. 1977. Influence of bovine growth hormone on growth rate, appetite, and food conversion of yearling coho salmon (Oncorhynchus kisutch) fed two diets of different composition. Can. J. Zool. 55:74–83.[Medline]
McLean, E., and E. M. Donaldson. 1993. The role of growth hormone in the growth of poikilotherms. Pages 43–71 in The Endocrinology of Growth, Development, and Metabolism in Vertebrates. M. P. Schreibman, C. G. Scanes, P. K. T. Pang, ed. Academic Press, New York, NY.
McLean, E., R. H. Devlin, J. C. Byatt, W. C. Clarke, and E. M. Donaldson. 1997. Impact of a controlled release formulation of recombinant bovine growth hormone upon growth and seawater adaptation in coho (Oncorhynchus kisutch) and chinook (Oncorhynchus tshawytscha) salmon. Aquaculture 156:113–128.
Moriyama, S., F. G. Ayson, and H. Kawauchi. 2000. Growth regulation by insulin-like growth factor-I in fish. Biosci. Biotechnol. Biochem. 64:1553–1562.[Medline]
Paloheimo, J. E., and L. M. Dickie. 1966. Food and growth of fishes: III. Relations among food, body size and growth efficiency. J. Fish. Res. Board Can. 23:1209–1248.
Peter, R. E., and T. A. Marchant. 1995. The endocrinology of growth in carp and related species. Aquaculture 129:299–321.
Peterson, B. C., B. C. Small, and B. G. Bosworth. 2004a. Effects of bovine growth hormone (Posilac®) on growth performance, body composition, and IGFBPs in two strains of channel catfish. Aquaculture 232:651–663.
Peterson B. C., G. C. Waldbieser, and A. L. Bilodeau. 2004b. IGF-I and IGF-II mRNA expression in slow and fast growing families of USDA103 channel catfish (Ictalurus punctatus). Comp. Biochem. Phys. A 139:317–323.
Shamblott, M. J., C. M. Cheng, D. Bolt and T. T. Chen. 1995. Appearance of insulin-like growth factor mRNA in the liver and pyloric ceca of a teleost in response to exogenous growth hormone. Proc. Natl. Acad. Sci. USA 92:6943–6946.[Abstract/Free Full Text]
Silverstein, J. T., W. R. Wolters, M. Shimizu, and W. W. Dickhoff. 2000. Bovine growth hormone treatment of channel catfish: strain and temperature effects on growth, plasma IGF-I levels, feed intake and efficiency and body composition. Aquaculture 190:77–88.
Sjogren, K., J. L. Liu, K. Blad, S. Skrtic, O. Vidal, V. Wallenius, D. LeRoith, J. Tornell, O. G. Isaksson, J. O. Jansson, and C. Ohlsson. 1999. Liver-derived insulin-like growth factor I (IGF-I) is the principal source of IGF-I in blood but is not required for postnatal body growth in mice. Proc. Natl. Acad. Sci. USA 96:7088–7092.[Abstract/Free Full Text]
Small, B C., and B. C. Peterson. 2005. Establishment of a time-resolved fluoroimmunoassay for measuring plasma insulin-like growth factor I (IGF-I) in fish: Effect of fasting on growth hormone (GH) in channel catfish (Ictalurus punctatus). Domest. Anim. Endocrinol. 28:202–215.[Medline]
Vong, Q. P., K. M. Chan, and C. H. K. Cheng 2003. Quantification of common carp (Cyprinus carpio) IGF-I and IGF-II mRNA by real-time PCR: Differential regulation of expression by GH. J. Endocrinol. 178:513–521.[Abstract]
Wilson, R. P., W. W. Poe, T. G. Nemetz, and J. R. MacMillian. 1988. Effect of recombinant bovine growth hormone administration on growth and body composition of channel catfish. Aquaculture 73:229–236.
Windell, J. T. 1967. Rates of digestion in fishes. Page 151 in The Biological Basis of Freshwater Fish Production. S. O. Gerking, ed. Blackwell, Oxford, U.K.
Yakar, S., J. L. Liu, B. Stannard, A. Butler, D. Accili, B. Sauer, and D. LeRoith. 1999. Normal growth and development in the absence of hepatic insulin-like growth factor I. Proc. Natl. Acad. Sci. USA 96:7324–7329.[Abstract/Free Full Text]
This article has been cited by other articles:
|
|
|
|
 
M. E Picha, M. J Turano, C. K Tipsmark, and R. J Borski
Regulation of endocrine and paracrine sources of Igfs and Gh receptor during compensatory growth in hybrid striped bass (Morone chrysopsxMorone saxatilis)
J. Endocrinol.,
October 1, 2008;
199(1):
81 - 94.
[Abstract]
[Full Text]
[PDF]
|
|
|
Top
Abstract
Introduction
