Regulation of in vitro progesterone release from caprine luteal tissues by prostaglandins E2 and F2a

Luteal slices obtained from Day-10 cyclic, sexually mature, mixed-breed, superovulated goats were used to study the effects of prostaglandins E(2) and F(2)a (PGE(2) and PGF(2)a) on the release of progesterone. The goats were synchronized for estrus using a single intramuscular injection of 5 mg PGF(2)a given during the mid-luteal phase of the estrous cycle. Multiple follicular growth and superovulation were induced using a treatment regiment of follicle stimulating hormone (FSH) and luteinizing hormone releasing hormone (LHRH) previously standardized in our laboratory (1). The luteal slices were treated with PGE(2) or PGF(2)a at concentrations of 1 and 10 ng/ml each. Untreated luteal slices continued to release significant amounts of progesterone over the entire period of incubation (30 to 360 minutes). There was a progressive increase in progesterone accumulation following treatment with PGE(2) at both concentrations. The mean progesterone values were significantly higher in the PGE(2)-treated groups at all incubation periods than in the controls. Progesterone values at 10 ng/ml were higher (P<0.05) than at 1 ng/ml. Treatment with PGF(2)a decreased (P<0.05) progesterone release at 60 to 360 minutes of incubation compared with that of the corresponding controls for each incubation period. However, there appeared to be no differences (P>0.05) in mean progesterone values between the two concentrations of PGF(2)a. The results of this study showed that PGE(2) enhanced the release of progesterone by caprine luteal tissues, whereas PGF(2)a inhibited its release.