Effects of Dietary Salt and Angiotensin-Converting Enzyme Inhibitor on Atp-driven Ca Pump and Na/Ca Exchange in Aortic Rings of Dahl Rats

Abstract

We examined effects of dietary salt and cilazapril on ATP-driven Ca pump and Na/Ca exchange system in arterial smooth muscle of Dahl salt-sensitive (DS) rats. Twenty-four DS rats were assigned to 4 groups. H- and H+ rats were fed a high-salt diet. L- and L+ rats were fed a low-salt diet. H+ and L+ were administered cilazapril. Aortic rings were superfused with physiological saline, and isometric tension was measured. Relaxation rates of low-Na+-induced contractions were promoted by the removal of external Ca. Cilazapril significantly decreased blood pressure 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 relaxation 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 exchange and blood pressure. The results suggest that the decrease of Ca^2+> extrusion by the ATP-driven Ca pump resulting from a high-salt diet might lead to an elevation in the concentration of cellular Ca²⁺

Key Words:

• Dahl salt-sensitive rats
• dietary salt
• angiotensin-converting enzyme inhibitor
• cilazapril
• Na/Ca exchange
• ATP-driven Ca pump
• arterial smooth muscle