Altered pressor response to norepinephrine in calcium- and vitamin D-deficient rats.

Norepinephrine (NE: 100-1000 ng/kg) pressor response studies in calcium- (0.005, 0.17, 1.4, and 2.8% in diet) and vitamin D-supplemented (0, 95, 190, and 950 U vitamin D3/day) normotensive conscious male rats were performed prior to and after administration of propranolol (100 ng/kg). Eight weeks of the above dietary treatments (beginning at 4 weeks of age) increased blood pressure (B.P.) in the 0.005% Ca group but reduced it in the 2.8% Ca group compared with the 1.4% Ca (control) group, whereas infusion of NE produced increased and decreased pressor responses, respectively. In the vitamin D groups, B.P. was increased only in the 0 U group, but NE pressor response was decreased in all groups compared with the 190 U (control) group. Plasma and bone calcemic parameters reflected disturbed Ca metabolism due to Ca and vitamin D deficiencies and excesses. These data suggest that Ca and vitamin D-induced changes in B.P. regulation in rats may in part be due to an altered adrenergic system.