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Elimination of [¹⁴c] Heptachlor from Body Stores of Lactating Ewes Treated with Ovine Growth Hormone¹

New Mexico State University, Las Cruces 88003, Kansas University Medical Center, Kansas City 66103 and Institut fur Toxikologie, GSF-Munchen, Federal Republic of Germany

Abstract

Elimination of [¹⁴ C] heptachlor from body burdens of sheep was measured using mature ewes nursing single offspring, and the influence of exogenous ovine growth hormone (oGH) on elimination was studied. Six ewes (62 ± 2.5 kg BW) were dosed (i.p.) once with [¹⁴C] heptachlor (2.04 mg/kg BW; .88 µCi/mg heptachlor) and three were treated additionally with oGH (oGH; 5 mg/d) for 21 d. Three additional ewes served as controls. Excreta were collected each day for 21 d. Milk and blood were collected every 3rd d until ewes were euthanized at d 21. ¹⁴C activity was measured in excreta, milk, blood and tissues. Total cumulative activity of [¹⁴C] heptachlor and (or) metabolites in excreta (21 d) did not differ (P > .20) in ewes given oGH (25 ± 2%) vs none (23 ± 2%). Milk yield and protein content were unaffected (P > .10) by oGH. Ewes given oGH eliminated 2.2 ±.2% of total ¹⁴C dosage into milk during 21 d, whereas ewes untreated with oGH eliminated 1.3 ±.2% (P < .10); total ¹⁴C activity eliminated into milk plus excreta was similar for ewes given oGH or none (P > .10). For all six ewes, half-times (T_1/2) for distribution and elimination of ¹⁴C activity (heptachlor and metabolites) were 1.5 d and 11.7 d, respectively. Blood concentrations of ¹⁴C activity during 21 d yielded elimination half-time as 23 d. Unlike bovines, which eliminate heptachlor slowly (T_1/2 70 to 80 d) and mainly into milk fat, lactating ovines eliminated heptachlor and (or) metabolites mainly into excreta and about sixfold faster than bovines.

¹ Journal article 1378 of the New Mexico Agric. Exp. Sta., Las Cruces.

² Present address: Dept. of Anim. Sci., Univ. of Nevada, Reno 89557.

³ Dept. of Anim. and Range Sci. Appreciation is expressed to the National Hormone and Pituitary Program for supplying the oGH (NIDDK-oGH-12, AFP4015A) and assay materials [anti-oGH (NIDDKanti-oGH2, AFP-C012308); iodination grade oGH (NIDDK-oGH-I-3, AFP-52856)] used in this experiment. We also thank D. Rankins, W. Hoefler, C. Roberts, M. Alikhani, R. Reynolds, D. Kious and M. Hoefler for their assistance. Direct reprint requests to G. S. Smith.

⁴ Kansas Univ. Medical Center, Kansas City.

⁵ Institut fur Toxikologie, GSF-Munchen, Fed. Rep. Germany.