Three levels of dietary calcium-effects on blood pressure and electrolyte balance in spontaneously hypertensive rats.

The effects of three levels of calcium intake on blood pressure (BP) and electrolyte balance were studied for 12 weeks in spontaneously hypertensive rats (SHR): the chow of the SHR-1 group contained 1.1% calcium, and that of the supplemented groups 2.1% (SHR-2) and 3.1% (SHR-3) calcium. Wistar-Kyoto rats on a 1.1% calcium diet (WKY-1) served as normotensive controls. After 10 and 12 weeks BP was significantly lower in both calcium-supplemented groups than in the SHR-1 group, the SHR-2 and SHR-3 groups not deviating from each other. Platelets and lymphocytes were used as experimental cell models to study the effects of the calcium diets on intracellular free calcium ([Ca2+]i) level, which was measured by the fluorescent indicator quin-2. At the end of the study [Ca2+]i was lower in both cell types in SHR-2 and SHR-3 than in SHR-1, the supplemented groups being comparable to each other. In platelets [Ca2+]i still remained higher in the calcium-treated than the WKY-1 group, while in lymphocytes the levels were similar between SHR-2, SHR-3 and WKY-1. Plasma sodium, calcium and magnesium levels did not differ in the SHR groups, but plasma potassium was higher in both supplemented groups than in SHR-1. Plasma renin activity was comparable in SHR-1, SHR-2 and WKY-1, but was suppressed in the SHR-3 group. Creatinine clearance in the SHR-3 group was higher than in SHR-1 and SHR-2, but still remained lower than in WKY-1.(ABSTRACT TRUNCATED AT 250 WORDS)