Oviduct response to prostaglandins: Influence of estradiol and progesterone

Abstract

Oviductal motility was measured in the isthmus of ovariectomized New Zealand rabbits. The effects of estradiol and progesterone on spontaneous motility and on the response of the oviduct to exogenously administered prostaglandin E 1 (PGE 1) and PGF 2α were determined. Estradiol treatment significantly increased both the amplitude (P<0.05) and frequency (P<0.01) of spontaneous contractions. The amplitude of spontaneous activity was less following progesterone treatment than following estradiol treatment (P<0.05). Progesterone treatment increased the duration of oviduct response to PGE 1 (P<0.05). Estradiol treatment had no effect on the response to PGE 1. Increased oviductal activity caused by PGF 2α lasted significantly (P<0.01) longer in ovariectomized, untreated animals than in ovariectomized animals treated with estradiol or progesterone. Progesterone was more effective than estradiol in decreasing the duration of the response to PGF 2α. These effects of steroid hormones on the responsiveness of the oviduct to PGE 1 and PGF 2α could contribute to the physiological control of egg transport. The nadir of ovarian hormone influence, as in the recently ovariectomized animals and as occurs immediately after ovulation, is associated with a high responsiveness of the oviduct to PGF 2α. This could effectively increase isthmic occlusion and prevent the eggs from passing through the oviduct prematurely. The gradual increase in ovarian estradiol and progesterone secretion during the 3 1 2 days following coitus could result in decreased responsiveness to PGF 2α and increased responsiveness to PGE 1. These changes might cause relaxation of isthmic tone and allow movement of eggs through the isthmus into the uterus.