Control of contractility and the role of Na/Ca exchange in arterial smooth muscle.
Pharmacological tools were used to examine the "sources" of Ca for arterial smooth muscle (ASM) contraction. The influence of the transsarcolemmal Na gradient on the regulation of tension was also determined in small rings of rat aorta and bovine tail artery. Ryanodine plus a Ca channel blocker can be used to separate the portions of a contraction that are due respectively, to sarcoplasmic reticulum (SR) Ca release and to Ca entry through Ca channels. Manipulations that reduce the sarcolemmal Na gradient increase basal tone and augment the contractile responses to noradrenaline and caffeine; these manipulations also slow the rate of relaxation, in Ca-free solution, following induction of contractures. When Ca channels, alpha-receptors, and the Na pump are blocked, the contractile responses to K-rich media increase as the ASMs accumulate Na. These data indicate that a voltage-sensitive Na/Ca exchange system helps to regulate cell Ca in ASM.
Ashida
T
T
Department of Physiology, University of Maryland School of Medicine, Baltimore.
Blaustein
M P
MP
D000818:Animals; D001011:Aorta; D001158:Arteries; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002417:Cattle; D066298:In Vitro Techniques; D007474:Ion Exchange; D009119:Muscle Contraction / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D012433:Ryanodine / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism*; D013623:Tail / Q000098:blood supply
D002121:Calcium Channel Blockers; D012433:Ryanodine; D012964:Sodium; D002118:Calcium