Inhibition by angiotensin II of some vasopressin effects on renal function in sheep

The effects of intravenous infusions of arginine vasopressin (AVP) alone and with angiotensin II (AII) on renal function were studied in conscious Merino ewes. AVP at 11.5 pmol.min-1 caused an increase in water and electrolyte output which was associated with a rise in glomerular filtration rate (GFR), solute clearance, solute-free water reabsorption and tubular sodium reabsorption. Addition of AII of 100 ng.min-1 generally reversed all of these effects. The filtration fraction, which rose during AVP infusion, increased further when AII was added due to a greater fall in renal plasma flow than in GFR. The diuretic and electrolyte-excreting effects of infused AVP appeared to be brought about by an increase in GFR. It is suggested that this inappropriate effect of AVP, which is secreted in response to water deprivation, could be countered by the simultaneous production of AII.