Intracellular Sodium and Calcium in Vascular Smooth Muscle of Spontaneously Hypertensive Rats

Intracellular Na and Ca activities in arterial smooth muscle cells and red blood cells from normotensive and spontaneously hypertensive rats were measured by ion-selective electrodes. In red blood cells and aortic smooth muscle cells from spontaneously hypertensive rats examined immediately after isolation, intracellular Na and Ca activities were elevated. In aortic smooth muscle cells from spontaneously hypertensive rats, which had been cultured in artificial medium for 10–14 days, intracellular Na activity, but not intracellular Ca activity, was elevated. From these observations it is concluded that (a) increased intracellular Na activity is associated with a genetic disposition to hypertension, whereas humoral factors are necessary for intracellular Ca activity to be elevated; and (b) the electrolyte abnormalities in red blood cells from spontaneously hypertensive rats reflect concomitant changes in arterial smooth muscle, so that the findings in red blood cells can be regarded as reliable indicators of a generalized defect in cellular electrolyte metabolism.