Calcium efflux in rat tail artery during potassium induced relaxation

Abstract

The current study investigates the mechanism by which the concentration of activator Ca 2+ is decreased during potassium induced relaxation of vascular smooth muscle. Helically cut strips of rat tail artery were mounted between a fixed base and force transducers; isometric contractions were recorded. The arterial strips relaxed in response to potassium after contraction induced by norepinephrine in potassium-free solution. The efflux of 45Ca 2+ from the strips was stimulated by norepinephrine during the potassium-free cycle. This increase in efflux was prevented during potassium induced relaxation. D-600, an inhibitor of transmembrane Ca 2+ flux, reduced the magnitude of potassium induced relaxation by 35%. These observations suggest that relaxation in response to potassium is the result of a decrease in membrane permeability to Ca 2+ coupled with an increase in Ca 2+ sequestration at intracellular sites.