Renal effects of Val 5-angiotensin II-amide, vasopressin and diuretics in the rat, as influenced by water diuresis and by ethanol anesthesia

Abstract

In unanesthetized rats in water diuresis synthetic angiotensin II-amide (0.25–1.25 μg/kg·min) enhances sodium and water excretion without depressing clearance of free water (C H2O). When the drug is infused for more than 25 min, C H2O falls slightly but significantly in spite of continued natriuresis. Infussion of rat renin elicits similar effects. Neither high nor low doses of angiotensin depress urine flow in unanesthetized rats. The diuretic response to angiotensin in water diuresis, but not in isotonic saline diuresis is accompanied by, but is not due to, an increase of glomerular filtration rate (GFR). Pentobarbital anesthesia does not depress the diuretic response to angiotensin in water-loaded rats Ethanol anesthesia does not depress the diuretic response to angiotensin in water-loaded rats. During the first 10 to 20 min of infusion of angiotensin II amide GFR, sodium excretion and C H2O fall. With continued infusion, GFR reverts to normal, while sodium excretion increases less than in unanesthetized animals; simultaneously a ‘vasopressin-like’ depression of C H2O appears. Angiotensin, thus, possesses a tabular natriuretic and diuretic effect as well as a vascular anti-diuretic and anti-natriuretic effect and a tabular vasopressin-like anti-diuretic effect. Ethanol anesthesia enhances the anti-diuretic effect of angiotensin, and increases the sensitivity of water-loaded rats to the anti-diuretic action of vasopressin by approximately one order of magnitude, but does not influence the diuretic response to hydrochlorothiazide or to furosemide. The conditions which favor one or the other of the three types of renal effects of angiotensin in the rat, the dog or in man are discussed. There are similarities between the renal actions of angiotensin, of oxytocin and of vasopressin in the rat and perhaps also in other species. The intra-renal urea and electrolyte concentrations in water diuresis are not modified by angiotensin.