ENDOCRINE REGULATION OF OVIDUCT SECRETIONS IN THE RABBIT1

Abstract

A system for prolonged volumetric collection of oviduct secretions was applied to adult New Zealand White rabbits. The effect on oviduct secretion rate of castration, progesterone, and postcastration estrogen and/or progesterone treatment was evaluated. After castration, the rate of oviduct secretion fell reaching a plateau at about one-third the precastration level within 24-124 hours (mean 67 hours). The secretion rate of the castrate increased following estrogen administration. This effect was obtained with doses as low as 0.5 μg. By continuous daily administration of estrogen, the oviduct secretion rate could be increased to precastration levels. Control injections of sesame oil failed to produce a change. In the intact animal, a single injection of 3 mg. of crystalline progesterone in 0.1 ml. of sesame oil was followed by a decrease in secretion rate which was most pronounced on the second posttreatment day. The oviduct secretion rate was uniformly depressed in the estrogen primed castrate (2 μg. of estradiol 17β daily) by administration of 1 mg. of progesterone in 1 ml. of sesame oil twice daily for three days. The rate became lowest on the third day of treatment. Castrates receiving a similar dosage schedule of progesterone in the absence of estrogen failed to exhibit a decrease. The data presented justify the conclusion that the rate of secretion in the rabbit oviduct is under endocrine control.