Modification of platelet and lymphocyte calcium handling and blood pressure by dietary sodium and calcium in genetically hypertensive rats
Oshima, T.; Young, E.W.; Hermsmeyer, K.; McCarron, D.A.
Journal of Laboratory and Clinical Medicine 119(2): 151-158
1992
ISSN/ISBN: 0022-2143 PMID: 1740628 Document Number: 401364
Abnormal cellular calcium handling has been postulated to be involved in the pathogenesis of hypertension. To determine whether the blood pressure response to dietary manipulation of sodium level (as the chloride salt) and calcium level is associated with changes in cellular cation metabolism, the interactive effects of both dietary components on blood pressure and intracellular free calcium concentration ([Ca2+]i) in blood platelets and thymic lymphocytes, erythrocyte sodium content, and blood ionized calcium were examined in stroke-prone spontaneously hypertensive rats. Rats were fed low (0.3%) or high (3.1%) sodium and low (0.2%) or high (2.0%) calcium diet for 6 weeks. With the rats rceiving the high sodium-low calcium diet, systolic blood pressure was higher than with other diets, among which no difference was detected. Both basal [Ca2+]i and ionomycin (50 and 150 nmol/L) stimulated [Ca2+]i in platelets, and in lymphocytes, were higher with the high sodium-low calcium diet than with the others. Thus the high sodium diet elevated blood pressure and increased [Ca2+]i in the resting and stimulated state in both cell lines with the low-calcium but not the high-calcium diet. The high-sodium diet was associated with increased sodium content of erythrocytes, whereas manipulations of dietary calcium level had no effect on erythrocyte sodium content. Dietary calcium level had more of an effect on blood ionized calcium than did dietary sodium level. In combined diet groups, blood pressure was positively, significantly correlated with basal and ionomycin-induced [Ca2+]i in platelets (r = 0.64 and 0.67, respectively) and in lymphocytes (r = 0.53 and 0.60, respectively). In conclusion, a high sodium-low calcium diet raised blood pressure and altered cellular calcium metabolism in two different cell types. Effects of dietary sodium level are dependent on dietary calcium level. Diet-induced alterations in cellular calcium metabolism may be in part involved in mediating the blood pressure response to dietary sodium chloride level.