Ace inhibitors, thirst and salt appetite: An assessment of dose dependant effects in rats with heart failure induced by myocardial infarction

We have previously shown that water intake after water deprivation is increased in heart failure and that angiotensin receptor blockade reduces water intake and abolishes the difference in intake between normal controls and animals with heart failure. In the present study we examined the effects of low dose ACE inhibitor, high dose ACE inhibitor or placebo on the thirst and salt appetite of rats with heart failure versus controls following 24h of water deprivation. Heart failure was induced by coronary artery ligation with control animals undergoing a sham procedure. All rats cycled through each of the doses of ACE inhibitor in a randomised order. The ACE inhibitor was administered by intraperitoneal injection 1h prior to the return of water. Water was returned to the rats at the end of the 24h deprivation period and the amount consumed recorded for a 2h period. Rats were then given access to both water and 1.8% NaCl with the intakes of both measured over a 2h period. Analysis of variance revealed a significant heart failure effect for water intake and a significant ACE inhibitor effect for both water and saline intakes. There was a significant increase in the post deprivation water intake of heart failure rats compared to controls (P < 0.05), however a significant increase in the saline intake of rats with heart failure hasn’t been demonstrated. High dose ACE inhibition increased both post-deprivation salt (P < 0.001) and water (P = 0.002) intakes. We conclude that ACE inhibition increases post-deprivation salt and water intake, contrary to previous results, and that there is an increase in the post-deprivation water intake of rats with heart failure.