Ernst-Rudolf Krefting

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 microm 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.

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

Decreased intracellular Mg++ concentrations seem to be involved in the pathogenesis of primary hypertension. Of special interest is the smooth muscle cell with its electrolyte metabolism in primary hypertension, but also heart muscle cells and their Mg++ concentrations are of growing interest. Therefore, in aortic smooth muscle cells and striated heart muscle cells (left ventricle) from 20 spontaneously hypertensive rats (SHR) of the Münster strain and 20 normotensive Wistar-Kyoto rats (WKY), the intracellular Mg++ content was measured. The electron probe x-ray microanalysis technique was used to determine intracellular Mg++ concentrations under nearly in vivo conditions in aortic cryosections 3 microm thick and striated heart muscle cells 4 microm 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 80.3 +/- 5.9 mmol/ kg dry weight). In conclusion, the present study revealed that genetic hypertension in the spontaneously hypertensive rat is accompanied by significantly decreased intracellular Mg++ concentrations in vascular smooth muscle cells. In striated heart muscle cells, Mg++ content was not significantly different in SHR and WKY. Mg++ handling is different in vascular smooth muscle and striated heart muscle cells in WKY and SHR (P < .01).

Electron-probe X-ray microanalysis of sodium ion content in vascular smooth muscle cells from spontaneously hypertensive and normotensive rats.

In aortic smooth muscle cells from 12 spontaneously hypertensive rats (SHR) of the Münster strain and 11 normotensive Wistar-Kyoto rats (WKY), the intracellular Na+ content was measured by electron-probe microanalysis. Measurements were performed in aortic cryosections 3 microns thick; the Na+ content was 12.5 +/- 2.4 g/kg dry weight in SHR versus 6.96 +/- 1.1 g/kg dry weight in WKY (P less than 0.01). Thus, aortic smooth muscle cells from SHR are characterized by a markedly elevated intracellular Na+ content compared with normotensive cells. This may either be due to genetically determined disturbances in transmembrane Na+ transport or to a circulating factor affecting Na+ transport. Cellular Na+ handling may be disturbed in SHR aortic smooth muscle as it is in hypertensive blood cells.

Electron-probe X-ray microanalysis of magnesium and sodium ion content in vascular smooth muscle cells from spontaneously hypertensive and normotensive 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 in vascular smooth muscle cells. Therefore, in aortic smooth muscle cells from seven spontaneously hypertensive rats (SHR) of the Münster strain and seven normotensive Wistar-Kyoto rats (WKY), the intracellular magnesium and sodium content were measured by electron-probe X-ray microanalysis. Measurements were performed in aortic cryosections 3 µm thick. The magnesium ion content was 0.93±0.17 g/kg dry weight in SHR vs 1.14±0.12 g/kg dry weight in WKY (p<0.05). Vascular smooth muscle sodium ion content was measured at 6.85±0.59 g/kg dry weight in WKY and 12.47±1.62 g/kg dry weight in SHR (p<0.05). In conclusion, aortic smooth muscle cells from SHR are characterized by a markedly lowered intracellular magnesium ion content and increased sodium ion concentrations compared with normotensive cells. The results may be due to genetically determined disturbances in transmembrane magnesium and sodium ion transport. Cellular magnesium and sodium handling may be disturbed in SHR aortic smooth muscle as it is in hypertensive blood cells.