Intracellular Na+ and Ca2+ activities in aortic smooth muscle cells from spontaneously hypertensive rats

Elevations of intracellular Na+ and Ca2+ in essential hypertension have up to now only been demonstrated in blood cells. Therefore, intracellular Na+ and Ca2+ activities were determined in cultured aortic smooth muscle cells from nine spontaneously hypertensive rats of the Münster strain and from nine normotensive Wistar rats. Intracellular ion activities were determined by ion-selective electrodes. In muscle cells from spontaneously hypertensive rats intracellular Na+ activity was markedly elevated (P less than 0.01), whereas intracellular Ca2+ was not significantly different. This points to the preponderance of genetic causes for the elevation of intracellular Na+, whereas the disturbances in cellular Ca2+ metabolism may additionally require humoral factors to become manifest.