title: Hg2+-induced contracture in mechanically skinned fibers of frog skeletal muscle.
abstract: In mechanically skinned fibers of the semitendinosus muscle of bullfrogs, we examined the role of membrane sulfhydryl groups on Ca2+ release from the sarcoplasmic reticulum (SR). Hg2+, a sulfhydryl reagent (20-100 microM), induced a repetitive contracture of skinned fibers, and this contracture did not occur in skinned fibers in which the SR had been disrupted by treatment with a detergent (Brij 58). Procaine (10 mM), Mg2+ (5 mM), or dithiothreitol (1 mM) blocked the Hg2+-induced contracture. Ag+ or p-chloromercuribenzenesulfonic acid produced similar contractures to that induced by Hg2+. We conclude that Hg2+ releases Ca2+ from SR of a skinned fiber by modifying sulfhydryl groups on the SR membrane, and suggest that the Ca2+ released by Hg2+ may trigger a greater release of Ca2+ from SR to develop tension.
mesh_terms: D000818:Animals; D002122:Calcium Chloride / Q000494:pharmacology; D004229:Dithiothreitol / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D008274:Magnesium / Q000494:pharmacology; D015636:Magnesium Chloride; D008627:Mercuric Chloride / Q000494:pharmacology*; D009119:Muscle Contraction / Q000187:drug effects*; D009132:Muscles / Q000187:drug effects / Q000502:physiology*; D011343:Procaine / Q000494:pharmacology; D011892:Rana catesbeiana
chemical_list: D015636:Magnesium Chloride; D011343:Procaine; D004533:Egtazic Acid; D008627:Mercuric Chloride; D008274:Magnesium; D002122:Calcium Chloride; D004229:Dithiothreitol