PRE-OVULATORY PROGESTERONE IN THE PERIPHERAL BLOOD OF THE RABBIT1

Abstract

Progesterone levels were detd. by bio-assay of plasma from 1 cc. samples of peripheral blood drawn from 20 rabbits after mating or the injn. of gonado-tropin. Samples were taken from each animal at intervals of minutes, hours, or days. Little or no "bound" progesterone was present. "Free" progesterone appeared an avg. of 100 min. after mating and of 64 min. after intraven. admn. of gonadotropin, thus confirming indirect evidence that the rabbit secretes progesterone prior to ovulation. After progesterone appeared its blood concn. fluctuated widely and with little regularity of pattern during the 1st day and a half. Thereafter, however, in the 2 rabbits from which daily samples were taken for a week, the secretory patterns were similar.