A role for the angiotensin IV/AT4 system in mediating natriuresis in the rat

Angiotensin II (AngII) or Angiotensin IV (AngIV) was infused into the renal artery of anesthetized rats while renal cortical blood flow was measured via laser Doppler flowmetry. The infusion of AngII produced a significant elevation in mean arterial pressure (MAP) with an accompanying decrease in cortical blood flow, glomerular filtration rate (GFR), urine volume, and urine sodium excretion. The infusion of AngIV induced significant increases in renal cortical blood flow and urine sodium excretion, without altering MAP, GFR, and urine volume. Pretreatment infusion with a specific AT. receptor antagonist, DuP 753, blocked or attenuated the subsequent AngII effects, while pretreatment infusion with the specific AT, receptor antagonist, divalinal-AngIV, blocked the AngIV effects. These results support distinct and opposite roles for AngII and AngIV, i.e. AngII acts: as an anti-natriuretic agent, while AngIV acts as a natriuretic agent. (C) 2001 Elsevier Science Inc. All rights reserved.