The selective effects of indomethacin on contractile responses of the isolated rat uterus

These studies were initiated to examine the effects of indomethacin on uterine contractile responses to oxytocin, carbachol, bradykinin, angiotension II and isoproterenol. Isolated uterine horns used in this study were removed from immature (21 days old) ovariectomized Sprague-Dawley rats (40-50 gm). Pre-treatment of uterine horns with indomethacin (10(-3) M) for periods of 15,30,60,90, and 180 seconds resulted in maximal inhibition of oxytocin-induced contractions by 15 seconds. In an indomethacin dose-response study, oxytocin-induced contractions were completely eliminated by a dose of indomethacin of 10(-3) M. Utilizing doses of indomethacin (3.5 X 10(-4) and 5.0 X 10(-4) M) that significantly reduced oxytocin-induced contractions by 48 and 77% respectively, contractile responses induced by carbachol (10(-6) M), bradykinin (10(-6) M), and angiotension II (4 X 10(-11) M) were not significantly reduced. Relaxation of uterine smooth muscle by isoproterenol (10(-5) M) in the presence of carbachol (10(-5) M) was not altered by indomethacin pretreatment. Data from this study demonstrate that indomethacin selectively inhibits oxytocin-induced uterine contractions in the immature rat.