[Molecular mechanisms of receptor-dependent signaling in the cells of the longitudinal and circular intestinal smooth muscles].

The G-protein-dependent intracellular signal cascades of excitation in longitudinal and circular intestinal smooth muscles (SM) are compared and summarized in the present review. The key mechanism of excitation in longitudinal SM is an activation of electro-mechanical coupling, in that G-proteins, phospholipase A2, arachidonic acid, membrane-bound cyclic adenosine diphosphoribose and Ca2+ are involved. We observed the role of arachidonic acid-activated chorine and voltage-dependent Ca2+ -channels (L-type) in Ca2+ mobilization in these muscle cells. In contrast to longitudinal, the main mechanism of agonist-induced excitation in circular SM is connected with activation of key methabotropical processes. The role of Rho-kinase in mechanisms of Ca2+ --sensitization of contractile apparatus in SM is also shown in this review. A comparative analysis of involvement of different links of signal cascades in initial and sustained phases of contraction in longitudinal and circular SM are also reviewed.