Modification of the contractile properties of rabbit skeletal muscle by ethylene glycol

The effect of ethylene glycol on the contractile properties of skeletal muscles was studied using glycerinated rabbit psoas muscle fibers. Measurements were made at an ionic strength of 0.2 M, pH 7.0, and at 10 degrees C. Ethylene glycol reversibly reduced isometric tension, active stiffness, the tension-to-stiffness ratio, and the shortening velocity at zero load (Vo) in a dose-dependent fashion. Ethylene glycol also reduced the Ca sensitivity for contraction. The extent of the reduction in Vo by ethylene glycol was much larger than that in the actomyosin ATPase activity reported by Travers and Hillaire (Eur. J. Biochem. 98, 293-299 [1979]). Although ethylene glycol reduced tension and Vo, the MgATP concentration dependence of these two quantities was almost unaffected. These results suggest that in the presence of ethylene glycol, force produced by crossbridges in the principal force-producing state is reduced and/or the relative population of the attached crossbridges in the low-force state increases. The results also suggest that the reduction in Vo by ethylene glycol is caused not only by a reduction in the actomyosin ATPase activity but also by a reduction in the shortening distance per mole of ATP split.