title: Force and ATPase rate in skinned skeletal muscle fibers.
abstract: Measurements of ATPase, force, and their ratio in chemically and mechanically skinned segments of muscle fibers provide a measure of steady-state kinetics of actomyosin interactions under force-generating conditions and thereby provide unique chemomechanical information. Preparations in which nonactomyosin ATPases are inhibited are available. The ratio of steady-state ATPase to steady-state isometric force (tension cost) was not altered significantly at different degrees of activation of contraction by Ca2+ or by shrinking the fiber lattice progressively to reduce force to zero. A fivefold decrease in tension cost was measured at low MgATP concentrations; data indicate either a decreased cross-bridge cycling time or an increased force per cross-bridge.
mesh_terms: D000205:Actomyosin / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001002:Anuria; D002118:Calcium / Q000494:pharmacology; D066298:In Vitro Techniques; D007700:Kinetics; D008433:Mathematics; D009119:Muscle Contraction; D009132:Muscles / Q000502:physiology*
chemical_list: D000255:Adenosine Triphosphate; D000205:Actomyosin; D000251:Adenosine Triphosphatases; D002118:Calcium