THE INDUCTION OF OVULATING HORMONE RELEASE FROM THE PITUITARY OF THE DOMESTIC HEN BY MEANS OF PROGESTERONE1

Abstract

An amt. of progesterone 10 times that required to induce ovulation in intact normal birds proved completely ineffective when injd. immediately after hypophysectomy; the dose required for normal birds, however, was completely effective when injd. immediately after sham hypophysectomy. Removal of the pituitary within 2 hrs. after the injn. of progesterone prevented ovulation from taking place. Hypophysectomy between 2 and 4 hrs. after injn. permitted increasing percentages of birds to ovulate, the same percentage as normal ovulating when hypophysectomy was delayed until 4 hrs. after the injn. The max. interval from hypophysectomy to actual or expected ovulation at which the max. percentage of birds ovulated was of the order of 4 to 6 hrs., which was the same value found for birds ovulating in response to a natural release of ovulating hormone. These facts justify the conclusion that progesterone induces a release of ovulating hormone from the pituitary of the chicken. The ovulation-inhibiting effect of progesterone described for mammals was demonstrated in the chicken also. Inhibition of ovulation in the latter follows progesterone injns. made at intervals of 36 hrs. or greater before an expected ovulation.