title: Effect of halothane on cardiac sarcoplasmic reticulum Ca2+-ATPase at low calcium concentrations.
abstract: The effect of halothane on cardiac sarcoplasmic reticulum Ca2+-ATPase activity was studied at low calcium concentrations (0.4-20 microM). Clinical concentrations of halothane (1%-3%, v/v) were found to depress Ca2+-ATPase activity more severely at lower calcium levels than at the higher calcium levels previously reported (greater than 0.1 mM). An increase in calcium concentration in the external medium of a preparation of isolated cardiac sarcoplasmic reticulum vesicles antagonized the halothane-induced depression of the Ca2+-ATPase activity. The depression of calcium-activated ATPase activity by halothane appears to take place by a competitive-type inhibition. The Ca2+-ATPase Vmax remained constant at 0.175 mumole/min/mg of protein with an increasing Km (0.47 microM-4.09 microM). Halothane depression of sarcoplasmic reticulum function may in part explain the ability of halothane to depress myocardial function.
mesh_terms: D000818:Animals; D002118:Calcium / Q000502:physiology*; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D002417:Cattle; D002462:Cell Membrane / Q000378:metabolism; D006221:Halothane / Q000494:pharmacology*; D066298:In Vitro Techniques; D007700:Kinetics; D008929:Mitochondria, Heart / Q000378:metabolism; D009200:Myocardial Contraction / Q000187:drug effects; D009206:Myocardium / Q000201:enzymology*; D012519:Sarcoplasmic Reticulum / Q000201:enzymology*
chemical_list: D000252:Calcium-Transporting ATPases; D002118:Calcium; D006221:Halothane