Intracellular Mg++ concentrations in smooth and striated muscle cells in spontaneously hypertensive rats

Decreased intracellular Mg++ concentrations seem to be involved in the path ogenesis of primary hypertension. Of special interest is the smooth muscle cell with its electrolyte metabolism in primary hypertension, but al:so hea rt muscle cells and their Mg++ concentrations are of growing interest. Ther efore, in aortic smooth muscle cells and striated heart muscle cells (left ventricle) from 20 spontaneously hypertensive rats (SHR) of the Munster str ain and 20 normotensive Wistar-Kyoto rats (WKY), the intracellular Mg++ con tent was measured. The electron probe x-ray microanalysis technique was use d to determine intracellular Mg++ concentrations under nearly in vivo condi tions in aortic cryosections 3 mu m thick and striated heart muscle cells 4 mu m thick (Camscan CS 24 apparatus). Vascular smooth muscle Mg++ content was 36.4 +/- 3.1 mmol/kg dry weight in SHR versus 48.6 +/- 3.7 mmol/kg dry weight in WKY (P < .001). In striated heart muscle cell Mg++ concentrations , there was no significant difference in SHR and WKY (79.9 +/- 5.6 versus 8 0.3 +/- 5.9 mmol/kg dry weight). In conclusion, the present study revealed that genetic hypertension in the spontaneously hypertensive rat is accompan ied by significantly decreased intracellular Mg++ concentrations in vascula r smooth muscle cells. In striated heart muscle cells, Mg++ content was not significantly different in SHR and WKY. Mg++ handling is different in vasc ular smooth muscle and striated heart muscle cells in WKY and SHR (P < .01) . (C) 2000 American Journal of Hypertension, Ltd.