Regulation of a Smooth Muscle Contraction: A Hypothesis Based on Skinned Fiber Studies
Although it is generally believed that smooth muscle will contract in response to an increase in cytosolic free calcium ion concentration, there is still considerable controversy concerning the explicit mechanism(s) coupling calcium to contraction. Bremel (1974), using filament displacement studies, showed that the Ca2+ dependence of vertebrate smooth muscle contraction is associated primarily with the thick filament. A few years later, Aksoy et al. (1976) and Sobieszek (1977) demonstrated that the Ca2+ sensitivity of acto-myosin ATPase activity was associated with phosphorylation of the 20 kDa myosin light chain (MLC) which was subsequently shown to result from activation of MLC kinase, a Ca2+ and calmodulin dependent enzyme (for reviews see Kamm and Stull, 1985; Hartshorne, 1987). Correlations have been shown between MLC phosphorylation and both Ca2+ dependent actin-activated myosin ATPase activity (Dabrowska et al., 1978; DiSalvo et al., 1978) and force development in either skinned (Kerrick et al., 1980; Chatterjee and Murphy, 1983) or intact (Barron et al., 1980; Driska et al., 1981) muscle fibers. These findings have brought about the widespread belief that this system is the primary regulator of smooth muscle contraction.
KeywordsMagnesium Glycerol Norepinephrine Sine Triphosphate
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- Aksoy, M. O., Murphy, R. A., Kamm, K. E., 1982, Role of Ca2+ and myosin light chain phosphorylation in regulation of smooth muscle, Am. J. Physiol, 242: C109.Google Scholar
- Butler, T. M., Siegman, M. J., Mooers, S. U., and Narayan, S. R., 1990, Myosin-product complex in the resting state and during relaxation of smooth muscle, Am. J. Physiol, 258: C1092.Google Scholar
- Chatterjee, M., Hai, C-M., and Murphy, R. A., 1987, Dependence of stress and velocity on Ca2+ and myosin phosphorylation in the skinned swine carotid media, in: “Regulation and Contraction of Smooth Muscle”, M. J. Siegman, A. P. Somlyo, and N. L. Stephens, eds., Alan R. Liss., New York, p. 399.Google Scholar
- Dillon, P. F. and Murphy, R. A., 1982, Tonic force maintenance with reduced shortening velocity in arterial smooth muscle, Am. J. Physiol, 242: C102.Google Scholar
- Hartshorne, D. J., 1987, Biochemistry of the contractile process in smooth muscle, in: “Physiology of the Gastrointestinal Tract”, L. R. Johnson, ed., Raven Press, New York, p. 423.Google Scholar
- Kerrick, W. G. L. and Hoar, P. E., 1987, Non-Ca2+-activated contraction in smooth muscle, in: “Regulation and Contraction of Smooth Muscle”, M. J. Siegman, A. P. Somlyo, and N. L. Stephens, eds., Alan R. Liss, New York, p. 437.Google Scholar
- Moreland, R. S. and Moreland, S., 1991, Characterization of magnesium-induced contractions in detergent-skinned swine carotid media, Am. J. Physiol., in press.Google Scholar
- Somlyo, A. P., Kitazawa, T., Himpens, B., Matthijs, G., Horiuti, K., Kobayashi, S., Goldman, Y. E., and Somlyo, A. V., 1989, Modulation of Ca2+-sensitivity and of the time course of contraction in smooth muscle: A major role of protein phosphatases?, in: “Adv. Prot. Phosphatases; Vol. 5”, W. Merleude and J. DiSalvo, eds., Leuven University Press, Leuven, p. 181.Google Scholar