Abstract
The role of potassium ions in the contraction of the vas deferens isolated from guinea-pig has been investigated herein. The preparation kept in an isotonic sucrose medium comprised of 0.07% sodium bicarbonate and 0.1% glucose was contracted by the addition of potassium ions at 5.6 mM, the concentration of which was the same as that in Locke's solution. When calcium ions, at any concentration, were used in place of potassium ions, the contraction was undiscernable, and when the calcium ion concentration exceeded 1.7 mM in the medium, the potassium induced contraction was depressed. This potassium induced contraction was not observable when the preparation had been pretreated by calcium-free Locke's solution, potassium-free Locke's solution, or strophanthin-G in large amounts. This contraction was seen even in the preparation, which had hardly responded to nicotine applied repeatedly. From these results, it is presumed that: potassium ions are essential for the initiation of smooth muscle contraction in the vas deferens, calcium ions present in the medium inhibit this potassium action, and smooth muscle contraction of vas deferens requires at least the presences of calcium ions, potassium ions, and ATP-ase activity in the tissue.
