BENEFICIAL-EFFECTS OF LONG-TERM ENALAPRIL TREATMENT AND LOW-SALT INTAKE ON SURVIVAL RATE OF DAHL SALT-SENSITIVE RATS WITH ESTABLISHED HYPERTENSION

We investigated the effects of long-term treatment with the angiotensi n-converting enzyme inhibitor enalapril and low-salt intake on the sur vival rate of Dahl salt-sensitive rats fed a high-salt (6.0% NaCl) die t. The systolic blood pressure of the rats increased gradually from 5 weeks of age and reached >240 mm Hg at 12 weeks of age. At this point, a low-salt diet group received a placebo (group 1, n = 10), and the h igh-salt diet group was divided into three groups: those given a place bo with the high-salt diet (group 2, n = 15), those given a chow chang e from a high-to a low-salt diet with a placebo (group 3, n = 14) and those given enalapril (30 mg/kg/day p.o., group 4, n = 14). At 19 week s of age, all rats in group 1 were alive, and the survival rate of gro up 2 was only 40% (P < .001 vs. group 1). The survival rates of both g roups 3 and 4 were significantly better: 86% (P < .01 vs. group 2) and 93% (P < .01), respectively. This beneficial effect on mortality was accompanied by an amelioration of the elevated plasma creatinine and u rea nitrogen levels and a decrease in the glomerular sclerosis lesion scores in both groups. These results suggested that a high-salt conten t diet and the renin-angiotensin system are deterioration factors in l ethal renal damage and the limitation of the diet salt content and inh ibition of the renin-angiotensin system are important to improve the s urvival rate in high-salt-loaded hypertensive Dahl salt-sensitive rats .