Oxytocin receptors and parturition. III. Increases in estrogen receptor and oxytocin receptor concentrations in the rat myometrium during prostaglandin F2 alpha-induced abortion.

Abstract

Marked elevations in the concentrations of receptors for estrogen (E) and oxytocin (OT) in the rat myometrium occur during spontaneous labor. These increases appear to be correlated with a decrease in plasma progesterone (P). In this study we sought to determine if these same changes in plasma steroid and myometrial receptor concentrations can be made to occur prematurely when pregnancy is terminated with prostaglandin Fα, (PGF2α). The administration of PGF2α to rats on day 18 of pregnancy resulted in premature delivery on day 20. PGF2α-induced labor was associated with a rise in the concentration of myometrial receptors for E and OT. The administration of P to these rats inhibited the increases in concentration of receptors for E and OT on day 20 and prevented premature delivery. In contrast, PGF2α administration on day 15, when plasma P is near maximal, resulted in marginal changes in myometrial receptor concentrations and in uninterrupted pregnancy. PGF2α treatment on day 10 increased the concentration...