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 pre ssure with vasoconstriction and with vasodilation when pressure is decrease d. Such myogenic vasoconstriction provides a level of basal tone that enabl es 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 comp lexity 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 phosphoryl ation. The involvement of Ca2+ may extend to modulation of ion channels and release of Ca2+ from the sarcoplasmic reticulum, alterations in Ca2+ sensi tivity, and coupling between cells within the vessel wall. The purpose of t his brief review is to summarize the current literature relating to Ca2+ an d the arteriolar myogenic response. Consideration is given to coupling of C a2+ changes to the mechanical stimuli, sources of Ca2+, involvement of ion channels, and spatiotemporal aspects of intracellular Ca2+ signaling.