STRESS MODULATION BY ELECTROLYTES IN SALT-SENSITIVE SPONTANEOUSLY HYPERTENSIVE RATS

Dietary calcium (Ca) has been proposed for the nonpharmacologic treatm ent of hypertension. However, its effect on blood pressure (BP) is deb atable, and clinical intervention studies have not yet established a c lear trend. The authors studied literature results on the effect of nu tritional Ca on BP in spontaneously hypertensive rats (SHR) and normot ensive Wistar-Kyoto (WKY) controls, using the metaanalysis technique. Analysis of the data on inbred animals showed a clear effect of dietar y Ca on BP: Ca supplementation produced a significant decrease in SHR and WKY rats, whereas Ca deprivation induced a significant increase in SHR. Furthermore, the hypotensive action of dietary Ca was maximal in salt-sensitive SHR (SHR-S), especially when given a high sodium (Na)/ high Ca diet. Because the SHR-S may be more sensitive to stress than t he salt-resistant SHR, the possible modulation of stress sensitivity b y dietary Na and Ca in SHR-S was examined. High Ca regimens prevented salt-sensitive hypertension in SHR-S, with the high Na/high Ca diet be ing most potent in lowering BP. This BP reduction by Ca was paralleled by an attenuation of stress sensitivity, as measured by increased bod y temperature during immobilization stress. Therefore, stress sensitiv ity was heightened by dietary Na and diminished by dietary Ca (p < 0.0 5). It was concluded that salt and stress sensitivity in hypertension may be related phenotypes that are both modulated in parallel by dieta ry ions.