Spasmolytic effects of cadmium and zinc ions upon the guinea-pig isolated ileum preparation.

1. An investigation has been made of the effects of cadmium and zinc ions upon the contractile response of the guinea-pig isolated ileum to methacholine, histamine, potassium ion and a.c. field stimulation. The metal ions depress the response to all of these agents.2. Radioisotope studies showed that cadmium and zinc ions have very much larger apparent volumes of distribution than sorbitol, both within whole ileum and within strips of the longitudinal smooth muscle layer. The results of these studies were indicative of surface binding and/or intracellular accumulation of these ions.3. It is suggested that cadmium and zinc ions directly depress smooth muscle contractility in a non-specific manner. This action may result from their binding to or accumulation within the muscle cells.