期刊
AMERICAN JOURNAL OF OBSTETRICS AND GYNECOLOGY
卷 192, 期 2, 页码 458-463出版社
MOSBY-ELSEVIER
DOI: 10.1016/j.ajog.2004.07.077
关键词
myometrium; preterm; progesterone; tocolysis; B-2-agonists
Objective: To evaluate the effect of natural progesterone on the relaxant effect of ritodrine on pregnant human oxytocin-induced myometrial contractility. Study design: Isometric tension recordings were performed under physiologic conditions on isolated myometrial strips taken from low-risk term pregnant women undergoing elective cesarean section. Cumulative effects of natural progesterone (10(-11) to 10(-5) mol/L) on oxytocin-induced myometrial contractility were evaluated. Contractile activity following ritodrine exposure was also investigated in myometrium pretreated with natural progesterone. Results: Natural progesterone alone exerted a concentration-dependent relaxant effect on myometrial contractions. The concentration-response curve for ritodrine from natural progesterone pretreated myometrium was shifted to the left with a significant reduction (P < .01) of 50% of the maximal response, contraction amplitude (P < .05), and frequency (P < .05). However, there was no significant difference in the mean maximal inhibition achieved (P =.95). Conclusion: Natural progesterone increased the relaxant effect of ritodrine by reducing 50% of the maximal response, amplitude, and frequency of myometrial contraction, most likely through nongenomic actions. These results suggest that natural progesterone may be beneficial for preventing preterm birth in a low-risk population. (C) 2005 Elsevier Inc. All rights reserved.
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