title: Calcium and excitation--contraction coupling in vascular smooth muscles.
abstract: The roles of Ca2+ in excitation--contraction coupling in vascular smooth muscle have been difficult to delineate, primarily because unambiguous association of specific Ca2+ components with morphologically defined cellular structures could not be attained. More recent use of washouts in La3+-substituted solutions at low temperature (to remove superficial Ca2+ and retain cellular Ca2+), Scatchard-coordinate plots (to identify incubation conditions appropriate for examining predominantly high or low affinity Ca2+ components), and high concentrations of Sr2+ (to remove high but not low affinity Ca2+) have facilitated qualitative and quantitative separation of different Ca2+ fractions. The release of high affinity Ca2+ elicited with norepinephrine and the increase in uptake of low affinity Ca2+ obtained with high K+ have been clearly demonstrated, and may directly measure or indirectly reflect changes in the level of intracellular free Ca2+. In other types of vascular smooth muscle (e.g., renal vessels, coronary arteries), similar Ca2+ components also appear to be present, but their relative size and functional importance for regulation of contractile responsiveness can differ.
mesh_terms: D000818:Animals; D001011:Aorta / Q000187:drug effects / Q000502:physiology; D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D004492:Edetic Acid / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects; D007811:Lanthanum / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D011188:Potassium / Q000494:pharmacology / Q000502:physiology; D011817:Rabbits; D013324:Strontium / Q000494:pharmacology
chemical_list: D007473:Ion Channels; D004533:Egtazic Acid; D007811:Lanthanum; D004492:Edetic Acid; D011188:Potassium; D002118:Calcium; D013324:Strontium