EFFECTS OF OUABAIN AND ALTERATIONS IN POTASSIUM CONCENTRATION ON SENSITIVITY TO DRUGS AND MEMBRANE-POTENTIAL OF SMOOTH-MUSCLE OF GUINEA-PIG AND RAT VAS-DEFERENS

Abstract

Partial depolarization of the smooth muscle cells were previously suggested to be an important factor in the post junctional supersensitivity induced in the guinea-pig vas deferens by chronic denervation or decentralization. Under acute in vitro conditions, the relationship between membrane potential changes and sensitivity in the vasa deferentia of guinea pigs and rats was studied. Sensitivity apparently was altered whenever resting potential was changed by 7-10 mV. Considerable electrophysiologic differences apparently exist between the smooth muscles of the guinea-pig and rat vas deferens. Ouabain or lowered external K caused a partial depolarization of the guinea-pig, but not the rat, vas deferens. The results, especially when combined with evidence that the rat vas deferens does possess a considerable amount of (Na+-K+)-ATPase, which is ouabain-sensitive, indicate that the Na pump is electrogenic in the guinea-pig, but not the rat, vas deferens.