Expression of Gsalpha, connexin-43, connexin-26, and EP1, 3, and 4 receptors in myometrium of prelabor singleton versus multiple gestations and the effects of mechanical stretch and steroids on Gsalpha.

OBJECTIVE: We tested the hypothesis that multiple pregnancies would be associated with altered expression of the following three groups of proteins that are key regulators of myometrial function: (i) Gsalpha, (ii) connexins-43 and 26, and (iii) prostanoid EP1, EP3, and EP4 receptors.

METHODS: An in vitro model was used to determine the effects of mechanical stretch on myometrial cell Gsalpha expression. Then the effects of the steroid hormones beta-estradiol and progesterone were tested on Gsalpha expression in vitro. All in vitro studies were performed using myometrium from nonlaboring women.

RESULTS: There were no differences in the expression of Gsalpha, prostaglandin E2 receptors, or gap junction proteins in myometrium of singleton versus multiple pregnancies. Mechanical stretch did not alter Gsalpha expression in vitro, and Gsalpha expression was unaffected by steroid hormones.

CONCLUSION: These results suggest that the methods whereby stretch can promote myometrial contraction are complex or require additional factors than those tested here. Alternatively, cases of multiple gestation that do not result in preterm labor perhaps compensate for the increased stretch by preventing aberrant expression of the proteins investigated in this study.