Ca2+ can affectV max without changes in myosin light chain phosphorylation in smooth muscle
- 1 August 1984
- journal article
- research article
- Published by Springer Nature in Pflügers Archiv - European Journal of Physiology
- Vol. 401 (4), 385-390
- https://doi.org/10.1007/bf00584340
Abstract
The effects of elevated [Ca2+]o on crossbridge cycling rate, measured as maximum velocity of shortening (V max) and high energy phosphate usage (Δ∼P), and on the degree of phosphorylation of the 20,000-dalton light chain of myosin (MyLCP) during an isometric tetanus were determined in the rabbit taenia coli at 18°C. In an normal Krebs medium (1.9 mM Ca2+) the average rate of Δ∼P during force development is 4xhigher than during force maintenance. In 4.5 mM Ca2+-Krebs, the average rate of Δ∼P increases by 100% during force development and during force maintenance above that observed in normal Krebs medium, with no significant change in force output.V max increased in the high Ca2+ medium, in good agreement with the corresponding rates of Δ∼P, but without any significant change in the degree of MyLCP. Also, in both high and low calcium media,V max decreased with tetanus duration as did the Δ∼P; however, the degree of phosphorylation was not directly related to the average rate of energy usage during the two phases of the tetanus. Therefore, in intact smooth muscles Ca2+-dependent and time-dependent changes inV max and average rate of Δ∼P can occur without corresponding changes in MyLCP. Modulation of crossbridge cycling rate may be accomplished by a Ca2+-dependent process in addition to MyLCP.This publication has 36 references indexed in Scilit:
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