Effect of Different Steroids on Lactating Rats. ∗

Abstract

Summary

The effect of different doses of estradiol, progesterone, testosterone and dehydroepiandrosterone on milk yield of normal lactating rats was assayed by daily s.c. injections of the steroids from day 7 to day 20 postpartum. It was found that high doses of estradiol (0.01–0.3 mg/kg/d) decrease milk secretion while a small dose of 0.001 mg/kg/d slightly increases it. Interruption of estradiol treatment on day 16 reestablished increased milk yield on day 20. Progesterone showed no significant decrease in milk yield at a dose of up to 100 mg/kg/d. Testosterone, and to a lesser degree dehydroepiandrosterone, were found to be potent inhibitors of milk secretion at a dose of 1 mg/kg/d while a low dose of 0.1 mg/kg/d failed to suppress milk production. The target organs of the above steroids are discussed.