Dietary sodium intake: Influence on calcium channels and urinary calcium excretion in spontaneously hypertensive rats

Binding of the 1,4-dihydropyridine [³H]PN200 110 was employed as an index of cardiac Ca²⁺ channels in normotensive (WKY) and spontaneously hypertensive (SHR) rats during 4 weeks of normal (0.73% NaCl) and high (8% NaCl) sodium diets when the rats were between 20 and 24 weeks of age. Binding site density was not different at the beginning of the study but was increased significantly (P < 0.01) after 1 week in the SHR on a high sodium diet; this difference was not apparent at 2, 3 or 4 weeks of the diet. During this same period, the urinary Ca²⁺ excretion in SHR was enhanced significantly (P < 0.01) and the urinary calcium/sodium ratio was elevated during the high sodium intake period.