J. Anim. Sci. 2002. 80:1888-1894
© 2002 American Society of Animal Science
Paylean alters myosin heavy chain isoform content in pig muscle1
F. F. S. Depreux2,
A. L. Grant1,
D. B. Anderson3 and
D. E. Gerrard4
Department of Animal Sciences, Purdue University, West Lafayette, IN 47907
4 Correspondence:
Smith Hall (phone: 765-494-8280; fax: 765-494-6816; E-mail:
dgerrard{at}purdue.edu).
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Abstract
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Feeding ß-adrenergic agonists promotes muscle growth. Early histological techniques failed to show precisely how feeding ractopamine-HCl (Paylean) alters muscle growth in pigs. To understand these effects, an indirect enzyme-linked immunosorbent assay (ELISA) was used to determine the abundance of each adult skeletal muscle myosin heavy chain isoform, one means of assigning muscle fiber type, in fast and slow muscles of pigs fed Paylean. Sixty growing pigs (
85 kg) were randomly assigned to three Paylean doses (0, 20, or 60 ppm). At 3, 7, 14, 28, and 42 d of treatment, four pigs per dose were harvested and white (WST) and red (RST) semitendinosus and longissimus (LM) muscles were removed and processed, and myosin heavy chain was quantified by ELISA. Feeding Paylean enhanced (P < 0.05) pigs’ average daily gain. Muscle myosin heavy chain (slow, 2A, 2AX, and 2B) composition differed (P < 0.05) across muscles. Compared with LM, RST contained approximately five times more (P < 0.0001) slow and type 2A myosin heavy chain and three times more 2AX myosin heavy chain but nearly undetectable amounts of 2B myosin heavy chain. Myosin heavy chain composition of the WST closely resembled that of the LM (i.e., greater 2AX and 2B and less slow and 2A). After 42d of 60 ppm Paylean, the amount of slow, 2A, and 2AX myosin heavy chain decreased (P < 0.05) across the three muscles whereas the amount of 2B myosin heavy chain increased (P < 0.05). In contrast, relative amounts of 2A and 2AX myosin heavy chain increased (P < 0.05) in muscle of control pigs at 42d. Changes associated with the 20-ppm dose were intermediate to and different from (P < 0.05) control and 60 ppm treatments. Correlations (P < 0.05) among various myosin heavy chain within muscles suggest that slow, type 2A, and 2X decrease with increases in 2B myosin heavy chain. These data show that administration of Paylean affects myosin heavy chain isoform composition in a time- and dose-dependent manner and provides a mechanism of action for Paylean altering animal growth.
Key Words: ß-Adrenergic Agonists • Muscle Fibers • Myosins
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Introduction
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Feeding ractopamine (Paylean), a phenethanolamine compound, or another ß-adrenergic agonist (BAA) improves average daily gain, stimulates muscle growth, and decreases fat content in pigs and several other species (Lands et al., 1967; Baker et al., 1984; Moloney et al., 1991). Administration of BAA increases muscle lactate dehydrogenase activity, decreases oxidative enzymes (Eisemann et al., 1987; Vestergaard et al., 1994a), and changes contractile properties (Zeman et al., 1988; Kim and Sainz, 1992; Van Der Heijden et al., 1998). In many species, there are four muscle fiber types in adults: type 1 (slow), 2A, 2X(D), and 2B (Schiaffino and Reggiani, 1994). Based on metabolic and ATPase staining, feeding BAA increases the cross-sectional area of type 2 (fast, glycolytic and oxido-glycolytic) muscle fibers in cattle, sheep, and rats (Kim et al., 1987; Wheeler and Koohmaraie, 1992; Vestergaard et al., 1994b), suggesting that BAA specifically targets type 2 fibers. There is a lack of understanding regarding the effect of BAA on the type 2 fiber subtypes. In pigs, and perhaps other species, the reason for this incomplete information may be that muscle fiber types classically identified as 2B muscle fibers actually include both type 2X(D) and type 2B fibers (Lefaucheur et al., 1998). Contribution of these fiber types alone accounts for approximately 80% of the total fibers in some pig muscles, yet the contribution of each 2X(D) and 2B fiber types to this total is difficult to discern because they are indistinguishable using classic histochemical staining techniques (Larzul et al., 1997). Recently, however, we have developed an immunological-based assay to quantify myosin heavy chain isoform content in muscle extracts (Depreux et al., 2000), which is related to fiber types. Therefore, the purpose of this study was to investigate the effects of Paylean over a 42-d period on the relative abundance of myosin heavy chain content in red and white muscles of pigs.
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Materials and Methods
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Animals and Experimental Design
Sixty growing, maternal line (Pig Improvement Co., Franklin, KY) pigs (85 kg) were randomly allocated to three Paylean treatment groups: 0, 20 (PL20), or 60 (PL60) mg/kg feed. All animals were managed under approved animal care and use guidelines. Pigs were fed an 18.5% crude protein, corn-soy diet. Four animals per treatment were harvested at 3, 7, 14, 28, and 42 d after beginning treatments. Immediately after exsanguination, longissimus muscle (LM) and portions of the red (RST) and white (ST) semitendinosus muscles were removed and quickly frozen in liquid nitrogen. Muscle samples were stored at -80°C until they were analyzed.
Myosin Extraction and Indirect ELISA
Myofibrillar proteins were extracted using established protocols (Bär and Pette, 1988). Extracted samples were diluted to 50% glycerol (vol/vol) and stored at -80°C. Total protein content was measured by the bichinchoninic acid method (Sigma Chemical, St Louis, MO). Relative abundance of muscle myosin heavy chain isoforms was determined using an indirect enzyme linked immunosorbent assay (ELISA), previously described by Depreux et al. (2000) using antibodies against type 1 (slow), 2A, 2AX, and 2B myosin heavy chain. Configuration of the ELISA resulted in absorbance (540 nm) values/microgram of extracted myofibrillar protein (Depreux et al., 2000). These values were normalized to pooled samples that were placed on each 96-well plate. Pooled samples were used to account for any possible plate-to-plate variation. Normalized absorbance values were used to reflect relative abundance of each myosin heavy chain.
Statistical Analysis
Statistical analysis was performed using general linear models procedure (SAS Inst. Inc., Cary, NC). Differences within a type of myosin heavy chain content only were analyzed using dose, time, and muscle and their interactions as factors.
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Results
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Pigs fed Paylean grew faster (P < 0.05) than control pigs (Table 1
). Pigs fed 60 ppm Paylean grew faster (P < 0.05) than pigs fed 20 ppm Paylean up to 2 wk, after which a dose effect was not observed.
To characterize myosin heavy chain composition among muscles used in this study, data were pooled across time and dose (Table 2). Relative amounts of myosin heavy chain isoforms differed (P < 0.001) across muscles. The average amount of slow myosin heavy chain was 5- and 20-fold greater in LM and RST, respectively, than in the WST. The abundance of 2A myosin heavy chain was greatest in the RST and was nearly three and five times that found in the LM and WST, respectively. Similarly, the amount of 2AX myosin heavy chain was the greatest in the RST, nearly two to three times that detected in the WST and LM. Conversely, the amount of 2B myosin heavy chain was the greatest in the LM, nearly double that found in the WST. The amount of 2B myosin heavy chain detected in the RST was low, likely below detection limits of the assay. A muscle x time interaction (P < 0.05) was observed for 2A myosin heavy chain (data not shown).
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Table 2. Relative abundance (arbitrary units) of slow, 2A, 2AX, and 2B myosin heavy chain isoforms in the red (RST) and white (WST) semitendinosus and in longissimus muscles (LM) pooled across time and dose
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A reduction in the relative abundance of 2A myosin heavy chain was observed (P < 0.05) with dose in the RST and WST but not LM (Table 3). With increasing Paylean dose, the amount of 2A myosin heavy chain decreased (P < 0.05) more than 20% in the RST and WST but did not change in the LM. The relative amount of slow (type 1) myosin heavy chain in muscle of treated pigs did not differ (Table 4). However, a time x dose interaction (P < 0.05) was observed for the relative amount of 2A, 2AX, and 2B myosin heavy chain isoform content in muscle of growing pigs fed ractopamine-HCl (Table 4). Muscle of PL60 pigs yielded changes in relative abundance of myosin heavy chain that was quite different from that observed in control pigs (Table 4). Specifically, the relative amount of 2A and 2AX myosin heavy chain decreased (P < 0.05), whereas the relative abundance of 2B myosin heavy chain increased (P < 0.05) by over 50% in muscle of PL60 pigs fed 42 d vs 3 d and by nearly 60% in muscle of control pigs vs PL60 pigs after 42 d of feeding. Changes in the relative abundance of various myosin heavy chain in muscle of PL20 pigs was intermediate to control and PL60 pigs. No three-way interactions were observed.
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Table 3. Effect of ractopamine-HCl dose pooled across time on the relative abundance (arbitrary units) of type 2A myosin heavy chain isoform in the red (RST) and white (WST) semitendinosus and in longissimus muscles (LM)
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Table 4. Effect of dose and time on the relative abundance (arbitrary units) of slow, type 2A, 2AX, and 2B myosin heavy chain isoform pooled across muscles of pigs fed ractopamine-HCl
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Significant correlation coefficients were observed between certain myosin heavy chain isoforms (Table 5). The correlation coefficient between 2A and 2AX contents was highest (r = 0.662, P < 0.0001) in RST and lowest (r = 0.326, P < 0.01) in LM. Inversely, the 2B and 2AX correlation coefficient was lowest in RST (r = -0.379, P < 0.001) and highest (r = -0.768, P < 0.0001) in LM. There was a positive correlation coefficient between 2A and slow myosin heavy chain content for RST and LM, but this was not significant in WST. The correlation between 2A and 2B content was highest in WST (r = -0.581, P < 0.0001) and lowest (r = -0.280, P < 0.01) in RST. Slow and 2B contents were negatively correlated (P < 0.05) in more white muscles (LM and WST), but not in the RST.
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Table 5. Correlation coefficients among myosin heavy chain isoforms (slow, type 2A, 2AX, and 2B) in the red (RST) and white (WST) semitendinosus and in longissimus (LM) muscles
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Discussion
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Effects of BAA on animal performance are well documented (Maloney et al., 1991). Although the exact mechanism underlying this augmented growth is unknown, BAA exert a direct effect on skeletal muscle growth (Kim and Sainz, 1992; Grant et al., 1993; Mersmann, 1998). Skeletal muscle is a collection of heterogeneous muscle fibers that possess different abilities to contract and metabolize energy (reviewed by Pette and Staron, 1997). In pig muscle, there are four adult muscle fiber types designated by their predominant myosin heavy chain isoform: 1 (slow), 2A, 2X(D), and 2B (Lefaucheur et al., 1998). The overall contribution of each fiber type dictates the contractile characteristics of the entire muscle. Because the functional demands on muscle can change, muscle fibers must have the capability to change their overall metabolism and contractibility in response to various stimuli (Pette and Staron, 1997). From a meat animal growth standpoint, animal performance is related to muscle fiber type composition (Sosnicki, 1987), and therefore changes in muscle fiber type composition have been proposed as a modulator of animal growth. Data most often cited to support this hypothesis include the dramatic differences reported in muscle fiber types between feral and domesticated pigs (Rahelic and Puac, 1981; Weiler et al., 1995). Feral pigs have a muscle fiber type composition consisting of a higher percentage of fatigue-resistant, slow-contracting, oxidative muscle fibers. Given the environmental selection pressures placed on feral pigs, development of a musculature capable of prolonged use was likely more advantageous for survival than larger muscle that was more easily fatigued. Additional support for this hypothesis can be drawn from the data showing that rats selected for rapid postnatal weight gain have more fast-contracting fibers (Swatland and Cassens, 1972). Furthermore, muscles from animals with certain genetic anomalies (double-muscled cattle, callipyge sheep, and halothane-positive pigs) have been shown to have a greater proportion of fast, glycolytic muscle fibers (reviewed by Lefaucheur and Gerrard, 2000). In contrast, others have been unable to show that further selection of domesticated pigs for high lean growth modifies muscle fiber type composition (Karlsson et al., 1993; Larzul et al., 1997) or that the induced muscle fiber hypertrophy observed with growth hormone administration has any effect on muscle fiber type (Beermann et al., 1987; Solomon et al., 1991). However, many of these earlier studies utilized fiber-typing protocols, which could not distinguish all four adult muscle fiber types, especially 2X and 2B fibers, which represent nearly 80% of the total fibers in the longissimus muscle of pigs (Larzul et al., 1997). Although the aforementioned studies do not establish a cause-and-effect relationship between animal performance and muscle fiber type, the fact that protein turnover rates are lower in muscle consisting of greater amounts of white fibers (Dadoune et al., 1978; Laurent et al., 1978) supports the hypothesis that muscle fiber type composition of muscle affects domestic animal growth. It stands to reason, therefore, that administration of a "repartitioning agent" that increases muscle growth may do so by modifying muscle fiber type composition.
Paylean was administered in this study at doses above approved levels; nonetheless, pig performance (ADG) was enhanced by over 10%, which is consistent with Moloney et al. (1991). In this trial, Paylean altered myosin heavy chain composition in a dose-, time-, and muscle-dependent manner, by increasing type 2B myosin heavy chain isoform content and reducing the contribution of other myosin heavy chain isoforms. In control pigs, a significant decrease in 2B and increase in 2AX myosin heavy chain content was observed over time in all muscles. However, in Paylean-treated pigs, this relationship was reversed, and the change was especially evident in pigs fed Paylean 60 for 42 d. Consequently, it appears that Paylean changes myosin heavy chain content and possibly muscle fiber type composition toward a faster phenotype and suggests that at lower doses administration of Paylean likely prevents the normal age-related reduction in the myosin heavy chain found in 2B fibers.
The amount of 2AX myosin heavy chain reported here must be interpreted with caution because it has been reported that the monoclonal antibody (SC-71) used to detect 2X myosin heavy chain co-detects 2A myosin heavy chain in pig muscle (Depreux et al., 2000). Therefore, it is possible that in a muscle containing a high proportion of 2A myosin heavy chain, such as RST, 2X myosin heavy chain content may be underestimated. However, in muscles such as the LM and WST, in which the contribution of 2A is well below 10% of the total myosin isoform content (Oksbjerg et al., 1994; Henckel et al., 1997; Larzul et al., 1997), it is unlikely that this cross-reactivity dramatically influenced these results. Nonetheless, it remains possible that the 2X myosin heavy chain content may have been underestimated in the RST.
Another interesting observation was that 2B myosin heavy chain in control pigs peaked within the first 14 d of the study. In contrast, the 2B myosin heavy chain in muscle of pigs fed Paylean peaked 2 to 4 wk later than in the controls. These data suggest that Paylean may shift normal muscle fiber type composition to times later in the growth of the animal. Again, these data support the idea that Paylean increases growth efficiency by shifting the growth curve to that characteristic of a later-maturing animal. Additional work involving longer treatment periods would be necessary to determine whether 2B myosin heavy chain decreases after 42 d.
As mentioned earlier, these data cannot be directly compared with previous studies on porcine muscles due to a lack of distinction between 2X and 2B fibers in those studies. Furthermore, comparison of these data to data from other species fed BAA is complicated by the fact that muscle fiber type composition varies dramatically with species. Moreover, protocols used in this study target myosin heavy chain isoform content, which only accounts for part of the contractile nature of muscle fibers. Indeed, both classic histochemistry, which relies on selective inactivation of inherent ATPase activity, and immunodetection of whole muscle myosin heavy chain composition have advantages and disadvantages. One of the biggest advantages of classic histochemistry is that data can be expressed on a fiber basis. As a result, conclusions regarding "absolute" muscle fiber type composition, the percentage of total muscle fibers represented by each subtype (type 1, 2A, X, or B), can be drawn. These data reveal the contribution of each muscle fiber in conveying the overall changes observed in the muscle of pigs fed BAA. However, this advantage also limits data interpretation; this type of histological approach is flawed because all muscle fibers do not extend the entire length of a muscle. Therefore, the real impact of each fiber type to the overall nature of the whole muscle, even though statistically different, is not known using this approach. In contrast, changes in the "relative" muscle fiber type composition can be assessed by determining the contribution of each myosin heavy chain isoform in a muscle sample and comparing differences within a myosin heavy chain isoform. Of course, this methodology provides little information regarding individual muscle fiber characteristics or the relative amount of each myosin heavy chain isoform within a muscle. These data, however, may be more representative and accurate of how the entire muscle changes in treated animals. Unfortunately, given the lack of other data generated using the latter approach, comparisons must be made to those studies using classic muscle fiber typing techniques. Aalhus et al. (1992) reported nearly a 5% increase in the percentage of 2B fibers in the semimembranosus and psoas major muscles of pigs fed Paylean at 20 ppm. In addition, Oksberg et al. (1994) observed an increase in the proportion of 2B fibers in the longissimus and biceps femoris muscles of pigs fed salbutamol. Differences in the BAA type and dose, as well as the genetics and weight of the pigs used, likely contribute to subtle discrepancies among BAA studies but clearly suggest that the absolute, and perhaps the relative, muscle fiber type composition is altered in treated animals. Results of our study show that Paylean affects myosin heavy chain content or relative muscle fiber type, which is consistent with changes observed in absolute muscle fiber type in earlier studies with pigs (Aalhus et al., 1992; Oksbjerg et al., 1994) and other species (Kim and Sainz, 1992; Vestergaard et al., 1994a).
The exact means by which myosin heavy chain isoform content is changed in response to BAA treatment is not fully known. However, changes in muscle fibers, as well as myosin heavy chain isoform content, follow a well-documented transition pathway: slow (1) 3 2A 3 2X 3 2B (reviewed by Schiaffino and Reggiani, 1994; Pette and Staron, 1997). Therefore, if the content of one myosin heavy chain isoform changes in a given amount of protein from a muscle sample, there will likely be a corresponding reduction in the content of another myosin heavy chain, if muscle fiber types are being converted as outlined above. Muscle samples collected in this study were subjected to a myosin extraction prior to ELISA. Therefore, changes in one myosin heavy chain should be observed in a corresponding change in another myosin heavy chain, as long as the changes were dramatic enough. Indeed, these types of changes in myosin heavy chain were evident in our study (Table 4
). Clearly, there was an increase in the abundance of 2B myosin heavy chain, relative to the amount found in muscle of control pigs at the same time. Coinciding with this increase, the abundance of 2A and 2X myosin heavy chain, relative to that found in muscle of control pigs, declined in muscle of pigs fed Paylean for 42 d. Furthermore, correlation coefficients among myosin heavy chain (Table 5) support this mechanism, especially regarding the equilibrium between 2B and 2AX myosin heavy chain. These reciprocal changes in myosin heavy chain isoforms located adjacent to each other in the transition pathway suggest BAA administration causes existing muscle fiber types to convert to another fiber type by producing a myosin heavy chain profile that is more indicative of a faster fiber type. Existence of transitory fibers co-expressing at least two types of myosin heavy chain isoform would support this hypothesis. In fact, Karlsson et al. (1993) reported the existence of such transitory fibers in normal, untreated pig muscle, indicating muscle fibers were changing via the aforementioned pathway. However, there has been no mention of such transitory fibers in earlier BAA studies. This may be due to the fact that these studies used classic histological techniques, which are more prone to error during categorical assignment of muscle fiber type, especially in pig muscle.
In contrast, if type 2 muscle fibers are truly the primary target of BAA and BAA-stimulated hypertrophy of these fibers in pig muscle, as postulated to occur in rats and cattle (Zemen et al., 1988; Vestegaard et al., 1994b; Criswell et al., 1996), then the BAA-induced increase in type 2 myosin heavy chain content observed in the present study would result from such an event as well. Recently, Polla et al. (2001) attempted to address this issue using a combination of methodologies (myofibrillar ATPase, immunocytochemistry, and electrophoretic separation of myosin heavy chain isoforms) to study the changes in muscle due to BAA treatment. These researchers observed an increase in the proportion of type 2B myosin heavy chain and a corresponding reduction in 2X myosin heavy chain in the soleus and diaphragm muscles of rats fed clenbuterol. Unfortunately, fiber type changes were not observed in the whiter, tibialis muscle, which is similar in fiber type composition to the longissimus muscle of pigs (Larzul et al., 1997). The exact reason for this discrepancy may be due to the fact that extremely young rats were used in this study, which may have circumvented any changes in the later-maturing, whiter muscles. Regardless of whether BAA causes a conversion of one muscle fiber type to another, or simply causes hypertrophy in a subset of fast fibers and thereby alters myosin heavy chain profiles, our data show that the entire muscle of pigs fed BAA is altered to contain greater amounts of myosin heavy chain isoforms, those indicative of a faster contracting, whiter muscle fiber type composition. Resolving the issue of whether BAA acts to change the absolute or relative muscle fiber type composition in pig muscle will likely demand a detailed investigation of muscle samples using both traditional and immunoreactive fiber typing, as well as a whole muscle approach to assessing muscle fiber type, similar to that outlined by Polla et al. (2001). These types of studies remain to be conducted in pigs.
The mechanism by which Paylean exerts an effect on muscle myosin heavy chain content may be related, in part, to the differential regulation of ß-adrenergic receptors (BAR) in different muscles and fiber types. Originally, skeletal muscle was thought to contain only ß 2 receptors (Kim et al., 1991). In fact, ligand-binding studies have shown that ß 1 and 2 receptors exist in pig muscle (Spurlock et al, 1993; Mersmann, 1998), but Abe et al. (1993) suggested that ß 3 receptors may also exist in skeletal muscle. Slow muscles generally have more BAR than fast muscle (Zeman et al., 1988). Likewise, slow fibers have more receptors than 2A fibers, and 2A fibers have more receptors than 2B fibers (Martin et al., 1989; Martin et al., 1992). Therefore, decreases in the amount of 2A myosin heavy chain observed in the RST of our study as well as the preferential effect of clenbuterol on the soleus (Polla et al., 2001) may be explained by variations in BAR abundance. However, stimulation of type 2B myosin heavy chain content cannot be explained by receptor distribution. This is corroborated by the fact that there seems to be little relationship between muscle hypertrophy and BAR density (Kim and Sainz, 1992; Hoey et al., 1995). However, evidence regarding the functionality of receptors found on different muscle fiber types is lacking. Furthermore, the sensitivity of each receptor type to long-term down-regulation requires further investigation.
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Implications
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Feeding Paylean to pigs induces changes in relative myosin heavy chain composition in various muscles. These changes mainly involve increases in faster-contracting myosin that are associated with faster, whiter muscle fiber types and reduced protein turnover. These data provide a mechanism by which ß-adrenergic agonists induce muscle growth. Further investigations, however, are necessary to delineate how individual muscle fibers and ß-adrenergic receptors participate in modulating this phenomenon.
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Footnotes
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1 Purdue University Agricultural Research Programs Journal Paper No. 16,742. 
2 Current address: Cardiovascular Research Center, Massachusetts General Hospital-East, Boston, MA 02129.
3 Lilly Research Laboratories, Greenfield, IN 46140.
Received for publication October 24, 2001.
Accepted for publication February 25, 2002.
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Literature Cited
|
|---|
Abe, H., Y. Minokoshi, and T. Shimazu. 1993. Effect of a ß3-adrenergic agonist, BRL35135A, on glucose uptake in rat skeletal muscle in vivo and in vitro. J. Endocrinol. 139:479–486.[Abstract]
Aalhus, J. L., A. L. Shaefer, A. C. Murray, and S. D. M. Jones. 1992. The effect of ractopamine-HCl-HCl on myofibre distribution and morphology and their relation to meat quality in swine. Meat Sci. 31:397–409.
Bär, A., and D. Pette. 1988. Three fast myosin heavy chains in adult rat skeletal muscle. FEBS Lett. 235:153–155.[Medline]
Baker, P. K., R. H. Dalrymple, D. L. Ingle, and C. A. Ricks. 1984. Use of a ß-adrenergic agonist to alter muscle and fat deposition in lambs. J. Anim. Sci. 59:1256–1261.[Abstract/Free Full Text]
Beermann, D. H., W. R. Butler, D. E. Hogue, V. K. Fishell, R. H. Dalrymple, C. A. Ricks, and C. G. Scanes. 1987. Cimaterol-induced muscle hypertrophy and altered endocrine status in lambs. J. Anim. Sci. 65:1514–1524.[Abstract/Free Full Text]
Criswell, D. S., S. K. Powers, and R. A. Herb. 1996. Clenbuterol-induced fiber type transition in the soleus of adult rats. Eur. J. Appl. Physiol. Occup. Physiol. 74:391–396.[Medline]
Depreux, F. F. S., C. S. Okamura, D. R. Swartz, A. L. Grant, A. M. Brandstetter, and D. E. Gerrard. 2000. Quantification of myosin heavy chain isoform content in porcine muscle using an enzyme-linked immunosorbent assay. Meat Sci. 56:261–269.
Dadoune, J. P., A. Terquem, and M. F. Alfonsi. 1978. High resolution radioautographic study of newly formed protein in striated muscle with emphasis on red and white fibers. Cell Tiss. 193:269–282.
Eisemann, J. H., G. B. Huntington, and C. L. Ferrell. 1987. Effects of dietary clenbuterol on metabolism of the hindquarters in steers. J. Anim. Sci. 66:342–353.
Grant, A. L., D. M. Skjaerlund, W. G. Helferich, W. G. Bergen, and R. A. Merkel. 1993. Skeletal muscle growth and expression of skeletal muscle alpha-actin mRNA and insulin-like growth factor I mRNA in pigs during feeding and withdrawal of ractopamine. J. Anim. Sci. 71:3319–3326.[Abstract]
Henckel, P., N. Oksberg, E. Erlandsen, P. Barton-Gade, and C. Bejerholm. 1997. Histo- and biochemical characteristics of the longissimus dorsi muscle in pigs and their relationships to performance and meat quality. Meat Sci. 47:311–321.
Hoye A. J., M. M. Reich, G. Davis, R. Shorthose, and M. N. Sillence. 1995. ß2-adrenoceptor densities do not correlate with growth, carcass quality, or meat quality in cattle. J. Anim. Sci. 73:3281–3286.[Abstract]
Karlsson, A., A. Enfalt, B. Essen-Gustavsson, K. Lundstrom, L. Rydhmer, and S. Stern. 1993. Muscle histochemical and biochemical properties in relation to meat quality during selection for increased lean tissue growth rate in pigs. J. Anim. Sci. 71:930–938.[Abstract]
Kim, Y. S., Y. B. Lee, C. R. Ashmore, and R. H. Dalrymple. 1997. Effect of repartitioning agent cimaterolon growth, carcass and skeletal muscle characteristics in lambs. J. Anim. Sci. 65:1391–1399.
Kim, Y. S., and R. D. Sainz. 1992. Miniriview: ß-adrenergic agonists and hypertrophy of skeletal muscles. Life Sci. 50:397–407.[Medline]
Kim, Y. S., R. D. Sainz, P. Molenaar, and R. J. Summers. 1991. Characterization of beta 1- and beta 2-adrenoceptors in rat skeletal muscles. Biochem. Pharmacol. 42:1783–1789.[Medline]
Lands, A. M., F. P. Ludena, and H. H. Buzzo. 1967. Differentiation of receptors responsive to isoproterenol. Life Sci. 6:2241–2249.[Medline]
Larzul, C., L. Lefaucheur, P. Ecolan, J. Gogué, A. Talmant, P. Sellier, P. Le Roy, and G. Monin. 1997. Phenotypic and genetic parameters for Longissimus muscle fiber characteristics in relation to growth, carcass, and meat quality traits in Large White pigs. J. Anim. Sci. 75:3126–3137.[Abstract/Free Full Text]
Laurent, G. J., M. P. Sparrow, P. C. Bates, and D. J. Millward. 1978. Turnover of muscle protein in the fowl (Gallus domesticus): Rates of protein syhthesis in fast and slow skeletal muscle of the adult fowl. Biochem. J. 176:393–401.[Medline]
Lefaucheur, L., R. K. Hoffman, D. E. Gerrard, C. S. Okamura, N. Rubinstein, and A. Kelly. 1998. Evidence for three adult fast myosin heavy chain isoforms in type II skeletal muscle fibers in pigs. J. Anim. Sci. 76:1584–1593.[Abstract/Free Full Text]
Lefaucheur, L., and D. E. Gerrard. 1999. Muscle fiber plasticity in farm mammals. Proc. Am. Soc. Anim. Sci., 2000. Available at: http://www.asas.org/jas/symposia/proceedings/0307.pdf. Accessed May 2, 2001.
Martin, W. H., E. Korte, T. K. Tolley, and J. E. Saffitz. 1992. Skeletal muscle ß-adrenoceptor distribution and responses to isoproterenol in hyperthyroidism. Am. J. Physiol. 262:E504–E510.[Medline]
Martin, W. H., S. S. Murphree, and J. E. Saffitz. 1989. ß-Adrenergic receptor distribution among muscle fiber types and resistance arterioles of white, red and intermediate skeletal muscle. Circul. Res. 64:1096–1105.[Abstract/Free Full Text]
Mersmann, H. J. 1998. Overview of the effects of ß-adrenergic receptor agonists on animal growth including mechanisms of actions. J. Anim. Sci. 76:160–172.[Abstract/Free Full Text]
Moloney, A., P. Allen, R. Joseph, and V. Tarrant, 1991. Influence of beta-adrenergic agonists and similar compounds on growth. In: Advances in Meat Research. pp 455–513. Elsevier Science Publishing, New York.
Oksbjerg, N., P. Henckel, and T. Rolph. 1994. Effects of salbutamol, a ß2-adrenergic agonist, on muscles of growing pigs fed different levels of dietary protein. I. Muscle fiber properties and muscle protein accretion. Acta Agric. Scand. 44:12–19.
Pette, D., and S. Staron. 1997. Mammalian skeletal muscle fiber type transitions. Int. Rev. Cyto. 170:143–223.
Polla, B., V. Cappelli, F. Morello, M. A Pellegrino, F. Boschi, O. Pastoris, and C. Reggiani 2001. Effects of the beta(2)-agonist clenbuterol on respiratory and limb muscles of weaning rats. Am. J. Physiol. 280:R862–869.
Rahelic, S., and S. Puac. 1981. Fiber types in longissimus dorsi from wild and highly selected pig breeds. Meat Sci. 50:431–450.
Schiaffino, S., and C. Reggiani. 1994. Myosin isoforms in mammalian skeletal muscle. J. Appl. Physiol. 77:493–501.[Abstract/Free Full Text]
Solomon, M. B., R. G. Campbell, N. C. Steele, and T. J. Caperna. 1991. Effects of exogenous porcine somatotropin administration between 30 and 60 kilograms on longissimus muscle fiber morphology and meat tenderness of pigs grown to 90 kilograms. J. Anim. Sci.69:641–645.[Abstract]
Sosnicki, A. 1987. Association of micrometric traits on meat quality, fattening and slaughter traits in the pig. J. Anim. Sci. 64:1412–1418.[Abstract/Free Full Text]
Spurlock, M. E., J. C. Cusumano, and S. E. Mills. 1993. (-)-[3H]- Dihydroalprenolol binding to ß-adrenergic receptor population in porcine adipose tissue and skeletal muscle membrane preparations. J. Anim. Sci. 71:1778–1785.[Abstract]
Swatland, H. J., and R. G. Cassens. 1972. A brief study of muscle enlargement in the rat. J. Anim. Sci. 34:21–24.[Abstract/Free Full Text]
Van Der Heijden, H. F. M., P. N. R. Dekhuijzen, H. Folgering, L. A. Ginsel, and Van Herwaarden. 1998. Long-term effects of clenbuterol on diaphram morphology and contractile properties in emphysematous hamsters. J. Appl. Physiol. 85:215–222.[Abstract/Free Full Text]
Vestergaard, M., P. Henckel, N. Oksbjerg, and K. Sejrsen. 1994a. The effect of cimaterol on muscle fiber characteristics, capillary, and metabolic potentials of longissimus and semitendinosus muscles from young fresian bulls. J. Anim. Sci. 72:2298–2306.[Abstract]
Vestergaard, M., K. Sejrsen, and S. Klastrup. 1994b. Growth, composition and eating quality of Longissimus dorsi from young bulls fed the beta-agonist cimaterol at consecutive developmental stages. Meat Sci. 38:55–66.
Weiler, U., H. -J. Appell, M. Kermser, S. Hofacker, and R. Claus. 1995. Consequences of selection on muscle composition, A comparative study on gracilis muscle in wild and domestic pigs. Anat. Histol. Embryol. 24:77–85.[Medline]
Wheeler, T. L., and M. Koohmaraie. 1992. Effects of the beta-adrenergic agonist L644,969 on muscle protein turnover, endogenous proteinase activities, and meat tenderness in steers. J. Anim. Sci.70:3035–3043.[Abstract]
Zeman, R. J., R. Ludemann, T. G. Easton, and J. D. Etlinger. 1988. Slow to fast alterations in skeletal muscle fibers caused by clenbuterol, a ß2-receptor agonist. Am. J. Physiol. 254:E724–E732.
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Abstract
Introduction
