The effects of ouabain and alterations in potassium concentration on the sensitivity to drugs and the membrane potential of the smooth muscle of the guinea-pig and rat vas deferens.

Previous work has suggested partial depolarization of the smooth muscles cells to be an important factor in the post junctional supersensitivity induced in the guinea-pig vator in the post junctional supersensitivity induced in the guinea-pig vas deferens by chronic denervation or decentralization. The present experiments were undertaken to explore, under acute in vitro conditions, the relationship between membrane potential changes and sensitivity in the vasa deferentia of guinea pigs and rats. The results indicate that sensitivity was altered whenever resting potential was changed by 7 to 10 mV. The results also indicated that considerable electrophysiologic differences exist between the smooth muscles of the guinea-pig and rat vas deferens. Notably, ouabain or lowered external potassium 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+)-adenosine triphosphatase, which is ouabain-sensitive, indicates that under the conditions of these experiments the Na pump is electrogenic in the guinea-pig, but not the rat, vas deferens.