Ca2+ regulation of vascular smooth muscle.
Regulation of intracellular free Ca2+ concentrations in vascular smooth muscle is accomplished mainly by Ca2+ channels and ATP-dependent Ca2+ pumps in the plasmalemma and sarcoplasmic reticulum (SR). Ca2+ entry through the plasmalemma is apparently mediated by four different pathways: leak; receptor-operated Ca2+ channels; potential sensitive Ca2+ channels; and stretch-activated channels. The agonist releasable intracellular Ca2+ store appears to be identical with the SR. Evidence for the involvement of Ca2+-induced Ca2+ release and inositol-1,4,5-trisphosphate in the release of SR Ca2+ is discussed. Smooth muscle contractions induced by certain agonists may be further enhanced by inhibition of Ca2+ uptake by the SR and of active Ca2+ extrusion across the plasmalemma. At the moment it is not clear from a consideration of the Ca2+ regulatory mechanisms present in vascular smooth muscle how dietary Ca2+ affects vascular tone. The increased Ca2+ permeation through smooth muscle cell membranes of resistance arteries taken from spontaneously hypertensive rats may be relevant to this problem.
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002136:Calcium, Dietary / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism; D006801:Humans; D007473:Ion Channels / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism*; D009638:Norepinephrine / Q000494:pharmacology; D012519:Sarcoplasmic Reticulum / Q000378:metabolism
D002136:Calcium, Dietary; D007473:Ion Channels; D002118:Calcium; D009638:Norepinephrine