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  • Author: P. G. McDONALD x
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P. G. McDONALD and CYNTHIA DOUGHTY

Summary.

Female rats were given a single subcutaneous injection of either 10 or 100 μg testosterone propionate (TP) or dihydrotestosterone propionate (DHTP) on Day 1 or 5 of life (Day 1 = day of birth). Both TP and DHTP delayed vaginal opening on Day 1 and advanced vaginal opening on Day 5. Testosterone propionate, but not DHTP, induced constant vaginal cornification and polyfollicular ovaries in the majority of rats. Dihydrotestosterone propionate had no effect on the Receptivity Quotient (lordosis/mount ratio × 100), whereas 100 μg TP on Day 1 or 5 significantly lowered the Quotient compared to DHTP treatment. Both TP and DHTP were equally potent in preventing ovarian compensatory hypertrophy in unilaterally ovariectomized female rats. In addition, treatment with 200 μg DHTP daily did not prevent the ovarian weight increase in response to exogenous gonadotrophin. The significance of these observations are discussed with respect to the physiological rôle of DHT.

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P. G. McDONALD and M. T. CLEGG

Summary.

Circulating levels of lh have been determined in intact and ovariectomized ewes before, during and after progesterone treatment. Neither 20 nor 40 mg progesterone daily for 10 days decreased the serum lh concentration during treatment. Following withdrawal, elevated levels of lh occurred on Days 4 to 6 in both intact non-cycling and ovariectomized ewes. Intact ewes treated during the initiation of the breeding season showed depressed levels of lh and failed to respond to progesterone treatment. The injection of 40 mg of progesterone daily did not delay the time of occurrence of the peak in lh activity.