Effects of estradiol and indomethacin on the contractile activity of the isolated rat uterus.

The effects of estradiol (E2) on uterine contractility have been studied by continuous monitoring of the contraction of the whole horn and simultaneous determination of the production of prostaglandins (PG). In 70-minute experiments, uterine horns of ovariectomized rats released more prostaglandin E (PGE2) into the bath medium at the beginning (35 pg/min/mg) than at the end of incubation (4 pg/min/mg). However, the decrease in the contraction frequency (CF) was not as large (15%). Estradiol treatment decreased the uterine production of PGE2 and, at low Ca concentrations in the bath medium, it completely abolished spontaneous contractions. Prostaglandin synthesis in the whole organ of ovariectomized rat was inhibited by indomethacin. Spontaneous contractions decreased only at indomethacin concentrations 10 fold higher than those needed to obtain 90% inhibition of prostaglandin synthesis. The effect of high concentrations of indomethacin (10(-5)M) on the CF was calcium-dependent and not related to the inhibition of PG synthesis. The decrease in the CF during hormonal treatment does not seem to be correlated with the decrease in PGE2 production.