Effect of angiotensin II on urinary dilution in normal man

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Abstract
Free water clearance (CHH2O) was studied in five normal subjects and in a patient with diabetes insipidus before and during the infusion of angiotensin II (Ciba), .2 µg/min. With angiotensin, CHH2O fell markedly, with only small changes in urinary osmolality both in the normal subjects and in the patient with diabetes insipidus. The fall in CHH2O was accompanied by a fall in UNaV, effective renal plasma flow (ERPF), and glomerular filtration rate (GFR). A physiological dose of Pitressin (25 mU/hr) given after the angiotensin, abolished CHH2O and markedly increased urinary osmolality while UNaV, ERPF, and GFR returned toward normal. The results may be best explained as a direct effect of angiotensin on renal hemodynamics, to decrease filtered sodium and water. Reabsorption of an increased fraction of filtered sodium and water by the proximal tubule would limit the amount reaching the diluting segment of the nephron and excreted in the urine. A possible role for angiotensin in the impaired water excretion of certain disease states, such as Addison's disease and congestive heart failure was suggested.
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