Regulation of the Ca2+ Sensitivity of Vascular Smooth Muscle Contractile Elements
Ca2+ is assumed to be the primary regulator of vascular smooth muscle contractility (1). In addition, receptor stimulation may modulate the Ca2+ sensitivity of vascular smooth muscle myofilaments, probably due to activation of protein kinase C (PKC). Morgan and Morgan (2,3) were the first to measure tension simultaneously with intracellular Cat2+ concentration ([Ca2+]i) in strips of ferret portal vein, using the photoprotein aequorin. They found that α-adrenergic activation induced a peak of light emission during the period of force development which fell close to the basal value during force maintenance. It has also been reported that phorbol esters which activate PKC (4), induce contraction in intact vascular smooth muscle (5-9), and shift the pCa-tension curve to the left in permeabilized smooth muscle (10,11). Although these reports tend to support a role for PKC in enhancing Cat2+ sensitivity of vascular smooth muscle myofilaments, they fail to establish a clear link between receptors, G proteins, PKC and the myofilaments.
KeywordsSmooth Muscle Sarcoplasmic Reticulum Sodium Nitroprusside Myosin Light Chain Kinase Contractile Element
Unable to display preview. Download preview PDF.
- 3.Morgan JP, Morgan KG. Stimulus-specific patterns of intracellular calcium levels in smooth muscle of the ferret portal vein. J Physiol (Lond) 351: 155, 1984.Google Scholar
- 10.Itoh T, Kubota Y, Kuriyama H. Effects of phorbol ester on acetylcholine-induced Cat+ mobilization and contraction in the porcine coronary artery. J Physiol (Lond) 397: 401–419, 1988.Google Scholar
- 14.Kamm KE, Stull JT. Regulation of smooth muscle contractile elements by second messengers. Annu Rev Physiol 51: 299: 313, 1989.Google Scholar
- 18.Fujiwara T, Itoh T, Kubota Y, Kuriyama H. Effect of guanosine nucleotides on skinned smooth muscle tissue of the rabbit mesenteric artery. J Physiol (Lond) 408: 535, 1989.Google Scholar
- 20.Cassidy P, Hoar PE, Kerrick WGL. Irreversible thiophosphorylation and activation of tension in functionally skipped rabbit ileum strips by [35S]ATP- S. J Biol Chem 254: 1 1148, 1979.Google Scholar
- 22.Kitazawa T, Kobayashi S, Horiuchi K, Somlyo AV, Somlyo AP. Receptor coupled, permeabilized smooth muscle: role of the phosphatidylinositol cascade, G-proteins and modulation of the contractile response to Ca2+. JBiol Chem 264: 5339, 1989.Google Scholar
- 23.Morgan JP, Morgan KG. Alteration of cytoplasmic ionized calcium level in smooth muscle by vasodilators in the ferret. J Physiol (Lond) 357: 539, 1984.Google Scholar
- 37.Nishimura J, Khalil RA, van Breemen C. Evidence for increased myofilament Cat+ sensitivity in norepinephrine-activated vascular smooth muscle. Am J Physiol,in press.Google Scholar
- 40.Sellers JR. mechanism of the phosphorylation-dependent regulation of smooth muscle heavy meromyosin. J Biol Chem 260: 15815, 1985.Google Scholar
- 43.Kerrick WGL, Hoar PE. Non-Ca2+-activated contraction in smooth muscle, in: Regulation and Contraction of Smooth Muscle, M.J. Siegmanm A.P. Somlyo, and N.L. Stephens, eds., A.R. Liss, New York, 1987.Google Scholar
- 45.Gabella G. The force generated by a visceral smooth muscle. J Physiol (Lond) 263: 199, 1976.Google Scholar
- 48.DeFeo TT, Morgan KG. Calcium-force relationships as detected with aequorin in two different vascular smooth muscles of the ferret. J Physiol (Lond) 369: 269, 1985.Google Scholar