Effect of oral magnesium supplementation on blood pressure, platelet aggregation and calcium handling in deoxycorticosterone acetate induced hypertension in rats

Objective To study the effect of oral magnesium supplementation on blood pr essure, platelet aggregation and platelet calcium handling in deoxycorticos terone acetate (DOCA)-induced hypertension in rats. Design and methods Rats were divided into four groups of 20 each. Drug trea tments were given for a 6-week period. Control rats were vehicle treated. I n the second group, DOCA, 15 mg/kg, was injected subcutaneously twice weekl y with 1% NaCl used instead of drinking water. The third group was given ma gnesium oxide (MgO), 1 g/kg daily, orally by gavage. The fourth group was g iven MgO along with DOCA and 1% NaCl, Blood pressure and heart rate were measured weekly. Platelet aggregation, i ntracellular calcium, calcium uptake and calcium efflux studies were perfor med at the end of sixth week Serum magnesium concentration, plasma levels o f reactive nitrogen intermediates (RNI) and citrulline were also measured Results There was a significant rise in blood pressure in the DOCA-treated rats, Magnesium prevented the gradual rise in blood pressure when given alo ng with DOCA, but had no effect in normotensive rats. Heart rate did not sh ow any significant change, platelet aggregation was significantly reduced i n all the treatment groups compared to the control group. DOCA treatment pr oduced a significant increase in the intracellular calcium concentration as well as the calcium uptake compared to the control group. Magnesium supple mentation inhibited the increased intracellular calcium concentration and c alcium uptake in DOCA-treated rats. RNI and citrulline levels were elevated in all the treatment groups. Serum magnesium levels were significantly hig her in the magnesium-treated and DOCA plus magnesium-treated rats. Conclusions Magnesium supplementation prevents blood pressure elevation in DOCA hypertensive rats. These effects are associated with inhibition of pla telet calcium uptake and decreased intracellular free calcium concentration . J Hypertens 2000, 18:919-926 (C) Lippincott Williams & Wilkins.