Administration of chlorothiazide to rats for 9 weeks produces an increase of intracellular sodium and a decrease of intracellular potassium in skeletal muscle. However, in cardiac muscle, in the wall of mesenteric arterioles, in aortic wall, and in kidney there is no significant alteration in the amount of sodium, potassium, or chloride per unit of dry tissue weight. The water content of heart muscle, skeletal muscle, and kidney is not altered by chlorothiazide. The intracellular concentration of Na and K in heart muscle is likewise unaltered by chlorothiazide. However, chlorothiazide produces a highly significant 44% increase in the granularity of the juxtaglomerular cells. The data in general suggest that chlorothiazide decreases the volume of extracellular fluid, but does not reduce the content of intracellular Na. Extracellular K is reduced as well as the K inside skeletal muscle fibers. However, the amount of K inside cardiac muscle fibers is unchanged by chlorothiazide.
Ca2+handling ability of sarcoplasmic reticulum in cardiac muscle fibers
