Pathophysiologic role of calcium in the development of vascular smooth muscle tone

Recent information indicates that the intracellular ionized calcium concentration [Ca2+]i plays a regulatory role not only in determining the magnitude of vascular tone but also in regulating growth of vascular tissue. Studies on living vascular smooth muscle cells using the calcium indicator aequorin have revealed that the relation between [Ca2+]i and contraction of the vascular smooth muscle cell is complex. More than 1 intracellular kinase may be involved, leading to the coexistence of multiple excitation-contraction coupling pathways. However, it appears that all of these pathways may be calcium-dependent. It is not yet known whether the cause of human essential hypertension involves an elevated [Ca2+]i in the vascular smooth muscle cell. However, evidence is presented supporting the concept that a decreased [Ca2+]i in the hypertensive smooth muscle cell will lead to a decrease in vascular tone and total peripheral resistance, and possibly also antagonize the growth response of the vascular smooth muscle cell associated with the secondary effects of hypertension.