The Binding of Cadmium Ions to the Smooth Muscle of Guinea‐Pig Taenia Coli

Taenia coli was used to study the property of binding of Cd2+. The Scatchard plots of cadmium uptake showed that two qualitative Cd2+ binding sites (high and low affinity binding sites) exist in taenia coli. Decrease in Ca2+ concentration in the medium did increase the cadmium binding. The Scatchard analysis of Cd2+ binding in taenia coli at 4 degrees indicated a single class of binding sites (only high affinity binding sites). These findings suggest that the greater number of high affinity Cd2+ binding sites in taenia coli may relate to the binding to cell membrane. Further, it was postulated that some of low affinity binding sites in taenia coli may reflect intracellular accumulation, indicating the action on the contractile system.