Endocrine Abstracts

Preterm labour is a serious clinical problem in obstetrics, and affective treatment of this condition still far from satisfactory. The purpose of this in vitro study was to examine the effects of isradipine, a calcium channel antagonist, on oxytocin-induced contractions of myometrium. Myometral strips were removed from late pregnant (18th day) Wistar rats following decapitation and placed in a jacked tissue bath containing Krebs’ solution and isometric contractions were evaluated. After recording the oxytocin-induced contractions (control, n=7), increasing concentrations of isradipine were applied to the tissue bath cumulatively. Single dose of isradipine was also tested on oxytocin-induced contractions in cacium-free conditions. The amplitude, frequencies (number of contractions for 10-minute) and area under curve (AUC) of contractions were evaluated at 10 min intervals before and after applications of isradipine. Wilcoxon Signed Ranks Test was used for statistical analysis. Of 1 ng/ml isradipine had no significant effect on the frequency, amplitude or AUC compared to control. Of 10 ng/ml of isradipine caused a significant decrease only in the amplitude and AUC values compared to control (P<0.05). Inhibitory actions of isradipine on oxytocin-induced contractions were more prominent at 0.1 μg/ml which was significant for the frequency, amplitude and AUC values (P<0.05). Of 1 μg/ml of isradipine completely abolished the contractions. Similarly, a single dose (1 μg/ml) of isradipine completely abolished the contractions when the extracellular Ca²⁺ was removed. Data from this study demonstrate that isradipine have inhibitory affect on oxytocin induced myometrial contractions in late pregnant rats. This result may warrant further investigations on the clinical potential of this agent in treatment of preterm labour.