Signal transduction in smooth muscle -: Invited review:: Arteriolar smooth muscle mechanotransduction:: Ca2+ signaling pathways underlying myogenic reactivity

The smooth muscle of arterioles responds to an increase in intraluminal pressure with vasoconstriction and with vasodilation when pressure is decreased. Such myogenic vasoconstriction provides a level of basal tone that enables arterioles to appropriately adjust diameter in response to neurohumoral stimuli. Key in this process of mechanotransduction is the role of changes in intracellular Ca2+. However, it is becoming clear that considerable complexity exists in the spatiotemporal characteristics of the Ca2+ signal and that changes in intracellular Ca2+ may play roles other than direct effects on the contractile process via activation of myosin light-chain phosphorylation. The involvement of Ca2+ may extend to modulation of ion channels and release of Ca2+ from the sarcoplasmic reticulum, alterations in Ca2+ sensitivity, and coupling between cells within the vessel wall. The purpose of this brief review is to summarize the current literature relating to Ca2+ and the arteriolar myogenic response. Consideration is given to coupling of Ca2+ changes to the mechanical stimuli, sources of Ca2+, involvement of ion channels, and spatiotemporal aspects of intracellular Ca2+ signaling.