Magnesium supplementation attenuates, but does not prevent, development ofhypertension in spontaneously hypertensive rats

This study evaluated the effects of magnesium supplementation on the develo pment of hypertension in spontaneously hypertensive rats (SHR) and assesses the actions of magnesium on extracellular and intracellular Ca2+, Na+, and K+ status. Ten-week-old SHR (n = 72) and Wistar-Kyoto rats (WKY) (n = 60) were divided into four groups: WKY, Mg-WKY (WKY receiving 650 mg/L Mg2+ sup plementation), SHR, and Mg-SHR (SHR receiving Mg2+). Rats were studied for 17 weeks. Serum and erythrocyte Mg2+ and Ca2+ (measured by atomic absorptio n spectroscopy) and Na+ and K+ (measured by name photometry) were determine d every 3 or 4 weeks. From 13 weeks of age, blood pressure (BP) was signifi cantly elevated in SHR compared with age-matched WKY. BP was reduced (P < . 01) in SHR after 10 weeks of Mg2+ supplementation and at 27 weeks of age, b e in SHR was 218 (12 ma Hg v 184 +/- 9 mm Hg) in Mg-SHR. From 18 weeks of a ge, serum and intracellular Mg2+ levels were significantly lower (P < .05) and from 21 weeks of age, erythrocyte Ca2+ was significantly higher in SHR than in WKY. Mg2+ supplementation normalized intracellular Mg2+ and Ca2+ co ncentrations in SHR. BP was inversely correlated with erythrocyte Mg2+ (r = -0.74, P < .01) and positively correlated with erythrocyte Ca2+ (r = 0.78, P < .001). In conclusion, long-term Mg2+ supplementation significantly att enuates, but does not prevent, the development of hypertension in SHR. Furt hermore, intracellular Mg2+ deficiency and Ca2+ overload in SHR are normali zed by Mg2+ treatment. (C) 1999 American Journal of Hypertension, Ltd.