Age-dependent intracellular Mg++ loss of smooth muscle cells from the spontaneously hypertensive rats (SHR)

Whereas in blood cells decreased magnesium concentrations in essential hype rtension have often been described, only sparse data exist on intracellular magnesium 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 normotensive Wistar-Kyoto rats (WKY) aged 1, and 3, and 8 - 10 months, the intracellular magnesium content was measured . Electron-probe X-ray microanalysis was used to determine intracellular Mg ++ concentrations in aortic cryosections 3 mu m thick. The magnesium ion co ntent was 42 +/- 8 mmol/kg dry weight in SHR versus 44 +/- 7 mmol/kg dry we ight in WKY aged 1 month, 47 +/- 13 mmol/kg dry weight in SHR versus 48 +/- 19) mmol/kg dry weight in WKY aged 3 months, and 37 +/- 6 mmol/kg dry weig ht in SHR versus 47 +/- 4 mmol/kg dry weight in WKY aged 8 - 10 months (p < 0.05). Aortic smooth muscle cells from SHR are characterized by a signific antly lowered intracellular magnesium ion content in 8- to 10-month-old ani mals as compared with aged-matched normotensive animals. The results may be due to genetically determined disturbances in transmembrane magnesium tran sport systems. Additionally, a subgroup of young SHR exists showing low int racellular Mg++ concentrations with an age of 1 and 3 months, when hyperten sion becomes established. In conclusion, cellular magnesium handling may be disturbed in SHR aortic smooth muscle as it is in hypertensive blood cells .