Hormones and calcium: mechanisms controlling uterine smooth muscle contractile activity

The regulation of myometrial contraction is of paramount importance for the maintenance of pregnancy and for partunition. Understanding this regulatio n involves delineating the pathways that control myometrial contraction and relaxation and defining the regulation of these pathways. The pathways can be broken do on further into those signalling cascades controlling the con centration of intracellular free calcium (Ca-i(2+)) and those controlling t he contractile apparatus itself. This discussion focuses primarily on the f ormer and their regulation during pregnancy. In particular, cross-talk betw een the contractant and relaxant signalling pathways mediated through cycli c AMP is markedly changed at the end of pregnancy.