INFLUENCE OF SODIUM AND POTASSIUM IONS ON THE CONTRACTION INDUCED BY CALCIUM IONS IN GUINEA-PIG ISOLATED VAS DEFERENS

1. When guinea-pig isolated vas deferens was pretreated with 0·01% tetrasodium edetate in an isotonic sucrose medium and then transferred to an edetate-free sucrose medium, the addition of CaCl₂ (0·28–8·80 mmol/1) induced a contraction. 2. When the edetate-free sucrose medium was replaced by saline containing NaHCO₃ and glucose, the contraction induced by CaCl₂ was only slightly smaller than that obtained in the sucrose medium. 3. When the saline medium was replaced by Ca-free Locke's solution, the contraction induced by CaCl₂ was almost the same as that obtained in the saline medium. 4. When the Ca-free Locke's solution was replaced by Ca-free K-Locke's solution (in which NaCl and CaCl₂ were replaced by KCl), the contraction induced by CaCl₂ was almost the same as that obtained in the sucrose medium.