Effects of physiological levels of estradiol-17 beta and progesterone on oviduct edema and ovum transport in the rabbit.

Abstract

The effects of estradiol-17β (E2) and progesterone (P4) on edema and transport of surrogate ova were investigated in oviducts of intact-mated and steroid-supplemented castrate rabbits during the 72 h period following mating or injection of hCG. A supplemental steroid dose regimen was devised for both E2 and P4 that approximated plasma steroid levels observed in the rabbit following coitus. Transport was monitored by observing the movement of glass beads inserted into the ampulla 10 h after mating or hCG injection. Animals were killed at 0, 4, 8, 12, 24, 48, or 72 h postcoitum/hCG. The oviducts were trimmed and divided into three segments: the ampulla, isthmus, and ampullary-isthmic junction regions. Wet and dry tissue weights were recorded, and the degree of edema expressed as percent tissue water. Oviduct segments of animals killed 24, 48, or 72 h postcoitum/hCG were flushed to recover surrogate ova. Tissue water content increased (P<0.01) in all regions of the oviduct by 4 h postcoitum and remained elevated throughout the period of ovum transport. Oviducts of ovariectomized does treated with E2 alone had a similar degree of tissue edema, whereas concurrent treatment with E2 and P4 induced a less pronounced, yet significant (P<0.01), edemic response at 48 h postcoitum. Tissue water content was not significantly altered in oviducts of nontreated castrates or P4-supplemented does. The patterns of surrogate ovum transport through oviducts of castrate does treated with E2 and P4 were similar to those observed in intact, mated animals. Other treatments hastened or retarded ovum transport. Physiological plasma steroid levels were achieved by injection of steroids into ovariectomized rabbits, and egg transport was affected by such treatment. In addition, our data suggest that oviductal edema, induced by a preovulatory surge of E2, temporarily blocks ovum transport at the ampullary-isthmic junction, isthmus and uterotubal junction.