Blood pressure and hypothalamic norepinephrine and dopamine in calcium-deficient rats

The influence of dietary calcium (Ca) on systolic blood pressure (BP) and hypothalamic norepinephrine (NE), dopamine (DA) and DA metabolites dihydroxyphenylacetic acid (DOPAC), and homovanillic acid (HVA) concentrations was investigated in male Sprague-Dawley rats raised on diets containing 0.005, 0.17, 1.4, and 2.8% Ca for eight weeks starting at four weeks of age. Blood pressure was significantly higher in the 0.005% Ca and lower in the 2.8% Ca group respectively, compared with the control (1.4% Ca) group. Hypothalamic NE and DA were lower only in the 0.005% Ca group. DOPAC concentration was higher in both Ca-deficient and -excess groups. No change in HVA was observed in any group. Plasma Ca was reduced and parathyroid hormone (PTH) was increased in Ca-deficient groups, but plasma Ca and PTH were increased and decreased, respectively, (nondetectable) in the Ca-excess group. These results suggest that changes in BP due to altered dietary Ca metabolism may be due in part to altered adrenergic system, as well as to dietary-induced changes in calcium metabolism.