Comparative effects of ouabain on isolated papillary muscle from tree shrews, guinea-pigs and rats

Abstract

Abstract Inotropic effects of ouabain were investigated in the isolated papillary muscle preparations of the tree shrew (Tupaiaglis), guinea-pigs and rats. In the guinea-pig and shrew papillary muscles, ouabain at concentrations of 10−8 to 3 × 10−7 M caused a concentration-dependent positive inotropic response in a similar magnitude, while in the rat, ouabain at concentrations of 10−7 to 3 × 10−6 M elicited negative inotropic one. Either phentolamine or pindolol in a concentration sufficient to block the α- and β-adrenoceptors did not antagonize the positive inotropic effect of ouabain in the papillary muscle preparation of the shrews.