title: A weak negative inotropic effect of protamine sulfate upon the isolated canine heart muscle.
abstract: The direct effect of protamine sulfate upon myocardial inotropism was studied using an isolated canine heart muscle preparation. Isometric force (F) was decreased to 87.6 +/- 1.2% of control values by a concentration of 50 x 10(-3) g/L protamine, which is approximately equal to the estimated serum concentration of protamine when administered clinically in doses of 4 mg/kg. The decrease in F was accompanied by a decrease in the maximum velocity of force development (dF/dt) but no alteration in time to peak force. Administration of the preservative of protamine sulfate did not alter F and dF/dt. This suggests that protamine produces a direct negative inotropic effect, mediated by a decrease in intensity but not by a decrease in duration of the active state.
mesh_terms: D000818:Animals; D003864:Depression, Chemical; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D006321:Heart / Q000187:drug effects* / Q000502:physiology; D066298:In Vitro Techniques; D009200:Myocardial Contraction / Q000187:drug effects; D011479:Protamines / Q000494:pharmacology*
chemical_list: D011479:Protamines