Effects of oestradiol and progesterone on the in vitro production of prostaglandin F2alpha by the guinea-pig uterus.

1 The effects of oestradiol and progesterone on the production of F 2alpha by the guinea-pig uterus in vitro have been studied. 2 Ovariectomized guinea-pigs were treated with oestradiol benzoate, progesterone, or a combination of these hormones. The uteri were homogenized and incubated and the prostaglandin F2alpha produced was measured by radiommunoassay or combined gas chromatography-mass spectrometry (g.c.-m.s.). Oestradiol treatment or progesterone followed by oestradiol caused a significant increase in prostaglandin F2alpha synthesis compared with control values, whereas progesterone treatment caused no significant increase. 3 The uteri from guinea-pigs on day 7 of the oestrous cycle were split into four parts, and each part homogenized and incubated either alone or in the presence of oestradiol-17beta, progesterone, or a combination of these hormones. Prostaglandin F2alpha was measured by g.c.-m.s. Oestradiol was found to increase prostaglandin F2alpha synthesis by the uterus whereas progesterone had no effect. However, progesterone did inhibit the response to oestradiol. 4 Oestradiol treatment of the guinea-pig uterus causes an increase in capacity to produce prostaglandin F2alpha in vitro. The role of progesterone is difficult to interpret.