RESUMO
OBJECTIVE: To study the effect of oxytocin, misoprostol and nimodiping on expressions of L-type voltage dependent calcium channel (VDCC-L) alpha(1) and VDCC-L beta(2) mRNA in the myometrium and left ventricular myocardial cells of the late pregnant rats. METHODS: A reverse transcription polymerase chain reaction (RT-PCR) method was used to examine and quantitate VDCC-L alpha(1) and VDCC-L beta(2) mRNA expressions in the uterine myometrium and left ventricular myocardial cells of rats, which were divided into the nature labor group, oxytocin group (oxytocin inducing labor), misoprostol group (misoprostol inducing labor) and nimodipine group (active labor at 48 hours after administering nimodipine). RESULTS: (1) In the uterine myometrium, the levels of VDCC-L alpha(1) mRNA expression in the nature labor, oxytocin, misoprostol and nimodipine group were 0.800 3 +/- 0.165 9, 0.863 1 +/- 0.192 1, 0.812 0 +/- 0.173 4 and 0.742 6 +/- 0.182 6, respectively. No significant difference was found in the four groups (P > 0.05). The levels of VDCC-L beta(2) mRNA expression in the above four groups were 0.646 9 +/- 0.130 4, 0.506 2 +/- 0.147 2, 0.500 5 +/- 0.135 6 and 0.492 9 +/- 0.127 6, respectively. There was no remarkable difference between the nature labor group and the other three administering drugs groups (P > 0.05). (2) In the left ventricular myocardial cells, expressions of VDCC-L alpha(1) in the nature labor, oxytocin, misoprostol and nimodipine group were 0.662 5 +/- 0.180 1, 0.636 5 +/- 0.157 8, 0.591 7 +/- 0.141 3 and 0.542 6 +/- 0.143 6, respectively; the levels of VDCC-L beta(2) mRNA expression were 0.670 2 +/- 0.140 5, 0.606 2 +/- 0.143 9, 0.591 4 +/- 0.121 9 and 0.585 2 +/- 0.131 0, respectively. Although both the levels of VDCC-L alpha(1) and VDCC-L beta(2) mRNA expression in the nature labor group were a little higher than those in the other three experiment groups, the statistic difference was not noted (P > 0.05). CONCLUSIONS: Oxytocin, misoprostol or nimodipine can induce or inhibit labor through regulating expressions of VDCC-L alpha(1) and VDCC-L beta(2) mRNA in the rat uterine myometrium and it may not have an adverse effect on heart function of normal pregnant rats. VDCC-L may be the common channel of labor induced by internal or external factors.