Endogenous digitalis: Reality or myth?

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)

show abstract