Inhibitory effects of isradipine on uterine contractions in pregnant rats

Objective: To investigate the effects of isradipine, which is a calcium channel blocker, on late pregnant rats’ myometrium under in vitro conditions. Methods: Stripes were obtained from the myometriums of pregnant rats which were decapitated on the 18 days of gestation. The effects of isradipine on myometrium were investigated in four groups and four cumulative doses: 1 ng/ml, 10 ng/ml, 0.1 μg/ml, 1 μg/ml. Group 1: spontaneous myometrial contractions, Group II: myometrial contractions induced by oxytocin, Group III: myometrial contractions induced by prostaglandin, Group IV: myometrial contractions induced by oxytocin in calcium-free medium. Wilcoxon signed ranks test was used for the statistical analysis and p<0.05 was considered statistically significant. Results: Group 1: compared to the control group, 10 ng/mL and 0.1 μg/mL isradipine decreased the amplitude of uterine contractions. Group II: 0.1 μg/mL isradipine decreased the frequency of contractions (p=0.02). Isradipine decreased the amplitudes of contractions in the doses of 10 ng/mL and 0.1 μg/mL (p=0.02 for each dose). Group III: 0.1 μg/mL isradipine decreased the frequency of contractions (p=0.02). Isradipine decreased the amplitudes of contractions in the doses of 10 ng/mL and 0.1 μg/mL (p=0.02 for each dose). One μg/mL isradipine completely removed all spontaneous and induced contractions. Group IV: when compared to mediums with calcium, both amplitudes and frequencies of the contractions were found lower in this group (p<0.001). Isradipine was only used in the dose of 1 μg/mL and it completely removed all contractions. Conclusion: Isradipine inhibits in vitro myometrial contractions in late pregnant rats and it may be effective in preventing early labor.