Angiotensin-(1-7) can interact with the rat proximal tubule AT(4) receptor system.
This study was undertaken to identify the non-AT(1), non-AT(2) angiotensin receptor that mediates the ANG-(1-7) inhibitory action on rat proximal tubule transport processes. ANG-(1-7) inhibited nystatin-stimulated, ouabain-suppressible O(2) consumption (QO(2)) rates in freshly isolated rat proximal tubules (reflecting reduced basolateral Na(+)-K(+)-ATPase activity). Selective angiotensin-receptor subtype antagonists revealed that AT(1) and AT(4) receptors mediated the response of ANG-(1-7). Receptor autoradiography of the rat kidney demonstrated a high density of AT(1) and AT(4) receptors and no specific (125)I-ANG(1-7) binding sites. Competition assays in rat kidney sections indicated that ANG-(1-7) competed predominantly for the AT(1) receptor site, whereas its NH(2)-terminal-deleted metabolite, ANG-(3-7), competed primarily for the AT(4)-receptor site. Metabolism of (125)I-ANG-(1-7) in rat proximal tubules generated peptide fragments that included ANG-(3-7), with the pentapeptide producing a concentration-dependent inhibition of nystatin-stimulated proximal tubule QO(2) that was abolished by AT(4)-receptor blockade. These results suggest that the generation of ANG-(3-7) from the NH(2)-terminal metabolism of ANG-(1-7) caused the interaction of the parent peptide with the proximal tubule AT(4) receptor, which elicited a decrease in energy-dependent solute transport.
Department of Veterinary and Comparative Anatomy, Pharmacology and Physiology, College of Veterinary Medicine, Washington State University, Pullman, Washington 99164-6520, USA.
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Handa
D000803:Angiotensin I / Q000502:physiology*; D000804:Angiotensin II / Q000031:analogs & derivatives / Q000378:metabolism; D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D010101:Oxygen Consumption; D010446:Peptide Fragments / Q000502:physiology*; D051381:Rats; D011945:Receptors, Angiotensin / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*
C090830:AT4 receptor; D010446:Peptide Fragments; D011945:Receptors, Angiotensin; D000804:Angiotensin II; C014805:angiotensin II, Sar(1)-Thr(8)-; D000803:Angiotensin I; D012964:Sodium; C118790:angiotensin I (1-7)