Na+ and Mg2+ contents in smooth muscle cells in spontaneously hypertensiverats

Whereas in blood cells decreased magnesium concentrations-and increased sod ium concentrations in essential hypertension have often been described, onl y sparse data exist on cellular magnesium or sodium content and exchange in vascular smooth muscle cells. Therefore in aortic smooth muscle cells from 10 spontaneously hypertensive rats (SHR) of the Munster strain and 10 norm otensive Wistar-Kyoto rats (WKY) aged 8 to 10 months, the intracellular mag nesium and sodium content was measured. Electron-probe Xray microanalysis w as used to determine intracellular Mg2+ and Na+ concentrations in aortic cr yosections 3 mu m thick. The magnesium ion content was 0.90 +/- 0.15 g/kg d ry weight in SHR versus 1.15 +/- 0.10 g/kg dry weight in WKY (means +/- SD, P < .05). Vascular smooth muscle sodium ion content was 6.66 +/- 0.39 g/kg dry weight in WKY and 12.61 +/- 0.91 g/kg dry weight in SHR (P < .01). Aor tic smooth muscle cells from SHR are characterized by markedly lowered intr acellular magnesium ion content and increased sodium ion concentrations in animals 8 to 10 months old, compared with normotensive cells. The results m ay be due to genetically determined disturbances in transmembrane magnesium and sodium ion transport. (C) 1999 American Journal of: Hypertension, Ltd.