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Skeletal muscle force and actomyosin ATPase activity reduced by nitric oxide donor

1997; American Physiological Society; Volume: 83; Issue: 4 Linguagem: Inglês

10.1152/jappl.1997.83.4.1326

8750-7587

William J. Perkins, Young-Soo Han, Gary C. Sieck,

Cardiovascular Effects of Exercise

Perkins, William J., Young-Soo Han, and Gary C. Sieck.Skeletal muscle force and actomyosin ATPase activity reduced by nitric oxide donor. J. Appl. Physiol.83(4): 1326–1332, 1997.—Nitric oxide (NO) may exert direct effects on actin-myosin cross-bridge cycling by modulating critical thiols on the myosin head. In the present study, the effects of the NO donor sodium nitroprusside (SNP; 100 μM to 10 mM) on mechanical properties and actomyosin adenosinetriphosphatase (ATPase) activity of single permeabilized muscle fibers from the rabbit psoas muscle were determined. The effects of N-ethylmaleimide (NEM; 5–250 μM), a thiol-specific alkylating reagent, on mechanical properties of single fibers were also evaluated. Both NEM (≥25 μM) and SNP (≥1 mM) significantly inhibited isometric force and actomyosin ATPase activity. The unloaded shortening velocity of SNP-treated single fibers was decreased, but to a lesser extent, suggesting that SNP effects on isometric force and actomyosin ATPase were largely due to decreased cross-bridge recruitment. The calcium sensitivity of SNP-treated single fibers was also decreased. The effects of SNP, but not NEM, on force and actomyosin ATPase activity were reversed by treatment with 10 mMdl-dithiothreitol, a thiol-reducing agent. We conclude that the NO donor SNP inhibits contractile function caused by reversible oxidation of contractile protein thiols.