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/l) 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.