EFFECTS OF DIETARY SALT AND ANGIOTENSIN-CONVERTING ENZYME-INHIBITOR ON ATP-DRIVEN CA PUMP AND NA CA EXCHANGE IN AORTIC RINGS OF DAHL RATS/

We examined effects of dietary salt and cilazapril on ATP-driven Ca pu mp and Na/Ca exchange system in arterial smooth muscle of Dahl salt-se nsitive (DS) rats. Twenty-four DS rats were assigned to 4 groups. H- a nd H+ rats were fed a high-salt diet. L- and L+ rats were fed a low-sa lt diet. H+ and L+ were administered cilazapril. Aortic rings were sup erfused with physiological saline, and isometric. tension was measured . Relaxation rates of low-Na+-induced contractions were promoted by th e removal of external Ca. Cilazapril significantly decreased blood pre ssure in both the high- and low-salt diet groups. Salt loading reduced relaxation rates in 1.2 mmol/l Na+, and enhanced the increase in rela xation rates from 1.2 mmol/l to normal Na+. A negative correlation was observed between Ca extrusion by the Ca pump and blood pressure, and a positive correlation was observed between Ca extrusion by Na/Ca exch ange and blood pressure. The results suggest that the decrease of Ca2 extrusion by the ATP-driven Ca pump resulting from a high-salt diet m ight lead to an elevation in the concentration of cellular Ca2+.