Inhibitory effects of L-type Ca2+-channel blocker nifedipine and magnesium sulfate on uterine contractility of full term pregnant women / 第二军医大学学报

ABSTRACT

Objective: To investigate the inhibitory effects of L-type Ca2+-channel blocker nifedipine and magnesium sulfate on uterine contractility of full term pregnant women and its relation with labour. Methods: Myometrial strips, prepared from biopsies taken at caesarean section from labouring and non-labouring women at full term pregnancy,were mounted in organ chambers for isometric tension recording. Oxytocin(10-9mol/L) was employed to induce stable contraction. The cumulative effects of nifedipine(10-8, 10-7, 10-6 and 10-5mol/L) and magnesium sulfate (1, 2, 4, 8 and 16 mmol/L) were studied by calculating the frequency, amplitude and AUC of contractions before and after drug applications, and the inhibitory rates were also calculated. Results: Nifedipine exerted a concentration-dependent relaxant effect on human term pregnant myometrial contractions induced by oxytocin. The relaxant effect was greater in the myometrium of non-labouring than that in the labouring group(P0.05). Conclusion: Decreased inhibition of human uterine contractility by L-type Ca2+-channel blocker nifedipine in term labouring myometrium may reflect sensitivity changes of Ca2+-channel to nifedipine after the onset of labour. The inhibitory effects of Mg2+ are not affected by labour, suggesting that Mg2+ may also exert its effect on contractility through other pathways besides Ca2+-channel.