Intracellular Na super(+) and Ca super(2+) activities in aortic smooth muscle cells from spontaneously hypertensive rats

Elevations of intracellular Na super(+) and Ca super(2+) in essential hypertension have up to now only been demonstrated in blood cells. Therefore, intracellular Na super(+) and Ca super(2+) activities were determined in cultured aortic smooth muscle cells from nine spontaneously hypertensive rats of the Muenster 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 super(+) activity was markedly elevated, whereas intracellular Ca super(2+) was not significantly different. This points to the preponderance of genetic causes for the elevation of intracellular Na super(+), whereas the disturbances in cellular Ca super(2+) metabolism may additionally require humoral factors to become manifest.