Na+ and Mg2+ contents in smooth muscle cells in spontaneously hypertensive rats

Whereas in blood cells decreased magnesium concentrations and increased sodium concentrations in essential hypertension have often been described, only 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 Münster strain and 10 normotensive Wistar-Kyoto rats (WKY) aged 8 to 10 months, the intracellular magnesium and sodium content was measured. Electron-probe X-ray microanalysis was used to determine intracellular Mg2+ and Na+ concentrations in aortic cryosections 3 μm thick. The magnesium ion content was 0.90 ± 0.15 g/kg dry 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). Aortic smooth muscle cells from SHR are characterized by markedly lowered intracellular magnesium ion content and increased sodium ion concentrations in animals 8 to 10 months old, compared with normotensive cells. The results may be due to genetically determined disturbances in transmembrane magnesium and sodium ion transport.