INCREASED NA-MUSCLE CELLS FROM SPONTANEOUSLY HYPERTENSIVE RATS( AND DECREASED MG2+ INTRACELLULAR CONCENTRATIONS IN VASCULAR SMOOTH)

1. Although in blood cells decreased magnesium concentrations and incr eased sodium concentrations in essential hypertension have often been described, only sparse data exist on cellular magnesium or sodium cont ent and exchange in vascular smooth muscle cells. 2. Therefore in aort ic smooth muscle cells from 10 spontaneously hypertensive rats (SHR) o f the Munster strain and 10 normotensive Wistar-Kyoto rats (WKY) aged 3 and 8-10 months, the intracellular magnesium and sodium content was measured. 3. Electron-probe X-ray microanalysis was used to determine intracellular Mg2+ and Na+ concentrations in aortic cryosections 3 mu m thick. The Mg2+ content was 47 +/- 13 mmol/kg dry weight in SHR vers us 48 +/- 19 mmol/kg dry weight in WKY aged 3 months, and 37 +/- 6 mmo l/kg dry weight in SHR versus 47 +/- 4 mmol/kg dry weight in WKY aged 8-10 months (P < 0.05). Vascular smooth muscle Nat content was 283 +/- 59 mmol/kg dry weight in WKY and 402 +/- 123 mmol/kg dry weight in SH R aged 3 months (P < 0.05), and 289 +/- 17 mmol/kg dry weight in WKY v ersus 548 +/- 39 mmol/kg dry weighs in SHR aged 8-10 months (P < 0.05) . 4. Aortic smooth muscle cells from SHR are characterized by a marked ly lower intracellular Mg2+ content in 8-10-month-old animals and incr eased Na+ concentrations compared with normotensive cells in 3- and 8- 10-month-old rats. The results may be due to genetically determined di sturbances in transmembrane Mg2+ and Nat transport. Cellular magnesium and sodium handling may be disturbed in SHR aortic smooth muscle as i t is in hypertensive blood cells. In addition, it is concluded that va scular smooth muscle cell Mg2+-Na+ exchanger can be altered in a subgr oup of SHR.