Functional bases for individualities among vascular smooth muscles

This review deals with cellular factors that contribute to individualities of vascular smooth-muscle function in different organ systems and at different levels of the vascular tree. Particular attention has been given to: (a) membrane receptors responsive to catechol-amines, serotonin, angiotensin II, dopamine, and ace-tycholine; (b) membrane properties, including resting and action potentials, and the Na⁺, K⁺ ATPase electrogenic pump; (c) regulation of cellular Ca²⁺; (d) contractile proteins; (e) metabolism, and (f) cell messengers. Differences in membrane receptors appear to be the major basis for the individualities found in various vascular smooth muscles. Differences in cell-membrane properties and Ca²⁺ regulation are also significant causes of variability. Cell metabolism and contractile proteins contribute relatively less to the individualities of vascular smooth muscle. Too little is known about cell messengers to assess their contribution to this individuality.