Inhibition of contraction by swelling of vascular smooth muscle in high KCl, low Na solution

Abstract

Rabbit aortic smooth muscle developed a contraction in a solution in which a part or all Na was replaced by equimolar K. Substitution of 80 mM NaCl with KCl produced a sustained contraction while the developed tension gradually declined in the solutions in which more than 120 mM NaCl was replaced by KCl. The decrease in the sustained tension was accompanied by an increase in tissue wet weight and both of the changes were prevented by a hyperosmotic addition of sucrose. Substitution for NaCl with K-propionate did not inhibit the sustained tension nor increased the wet weight of the tissue while substitution with KNO3 or KI produced a greater inhibition of the contraction than with KCl. It is suggested that the swelling of the rabbit aortic smooth muscle cells induced by the substituted KCl solution inhibits the contractility of the muscle.