Losartan (DUP-753) blocks the natriuretic, kaliuretic and antidiuretic effect of intracerebroventricular injection of carbachol in water-loaded rats

RESUMO

We determined the effect of intracerebroventricular (icv) administration of losartan, an angiotensin II NG II), subtype I receptor (AT1) antagonist, on icv carbachol-induced natriuresis, kaliuresis and antidiuresis in water-loaded male Holtzman rats (250-300 g) with a cannula implanted into the lateral ventricle (LV). The rats were water loaded with 5 per cent of their body weight by gavage twice, with the second gavage one hour after the first. Carbachol (2 nmol in mul) was injected icv immediately after the second load. When losartan (DUP753, 50 nmol in 1 mul) was administered icv, it was given 3 min before carbachol. Previous icv treatment with losartan significantly reduced the icv carbachol-induced natriuresis (324 ñ 17 muEq/120 min), kaliuresis (103ñ15muEq /120min) and antidiuresis(13.5ñ2.1 ml/120 min) compared to the effects of previous icv injection of saline (Na+ excretion = 498 ñ 22 muEq/120 min; K+ excretion = 167 ñ 20 muEq/120 min; urine volume = 5.2 ñ 1.2 ml/l20 min). These results, reported as means ñ SEM for 12 rats in each group, are consistent with the hypothesis that AT1 subtype receptors participate in the regulation of body electrolyte balance.