REGULATION OF UTERINE SMOOTH-MUSCLE FUNCTION DURING GESTATION

The uterus is unique among smooth muscular organs in that during pregn ancy it undergoes profound largely reversible changes orchestrated by the ovarian hormones. These changes facilitate uterine adaptation to t he stretch induced by the growing fetus such that a state of myometria l contractile quiescence can be maintained. This quiescent state usual ly is maintained until fetal development is sufficient for extrauterin e life, at which point unknown mechanisms precipitate conversion to a highly contractile state. Throughout pregnancy, signaling mechanisms f or myometrial contractility are altered-first to promote quiescence an d then again to promote contractions. The mechanisms responsible for t hese changes are only partially understood. This review attempts to su mmarize salient features of many of the changes in uterine contractile signaling and the current state of ongoing investigations of their me chanisms. We have also highlighted some newer information and concepts from nonuterine tissues, which we believe may provide insight into th e control of uterine smooth muscle function. Some detail has been omit ted, and can be found in the many excellent reviews cited. We hope tha t this discussion may stimulate the interests of other investigators. The diverse areas of inquiry offer hope that this decade will lead to a fuller understanding of myometrial function and the development of v astly improved approaches for the control of preterm labor.