Effect of prostaglandin E2 and its metabolites on lower segment myometrium in vitro.

The spontaneous activity of pregnant human lower segment myometrium has been studied in vitro using strips removed at cesarean section. Contractions were measured isometrically. During the 4-h experiments there was in increase in amplitude and decrease in frequency of contractions in control preparations. Prostaglandin F2 alpha (PGF2 alpha), its metabolites and prostaglandin E2 (PGE2) have been shown to be oxytocic in vivo, but there are no published data on the oxytocic effect of PGE2 metabolites. The effect on contractile activity of adding either PGE2 or one of its initial metabolites (15-keto-PGE2, 13,14-dihydro-15-keto-PGE2 or 13,14-dihydro-PGE2) or prostaglandin A2 (PGA2) to the tissue baths has been tested. No significant or consistent change in contractility was observed after the addition of any of the compounds tested. This probably indicates an inherent difference in the response of different portions of the uterine muscle, and cannot be taken to exclude activity in the intact uterus, particularly since PGE2 is a well-known oxytocic agent in vivo. The difficulty of working with this type of preparation is stressed, since there is wide variation in contractility as well as a constantly changing pattern.