title: ANG II AT2 receptor modulates AT1 receptor-mediated descending vasa recta endothelial Ca2+ signaling.
abstract: We tested whether the respective angiotensin type 1 (AT(1)) and 2 (AT(2)) receptor subtype antagonists losartan and PD-123319 could block the descending vasa recta (DVR) endothelial intracellular calcium concentration ([Ca(2+)](i)) suppression induced by ANG II. ANG II partially reversed the increase in [Ca(2+)](i) generated by cyclopiazonic acid (CPA; 10(-5) M), acetylcholine (ACh; 10(-5) M), or bradykinin (BK; 10(-7) M). Losartan (10(-5) M) blocked that effect. When vessels were treated with ANG II before stimulation with BK and ACh, concomitant AT(2) receptor blockade with PD-123319 (10(-8) M) augmented the suppression of endothelial [Ca(2+)](i) responses. Similarly, preactivation with the AT(2) receptor agonist CGP-42112A (10(-8) M) prevented AT(1) receptor stimulation with ANG II + PD-123319 from suppressing endothelial [Ca(2+)](i). In contrast to endothelial [Ca(2+)](i) suppression by ANG II, pericyte [Ca(2+)](i) exhibited typical peak and plateau [Ca(2+)](i) responses that were blocked by losartan but not PD-123319. DVR vasoconstriction by ANG II was augmented when AT(2) receptors were blocked with PD-123319. Similarly, AT(2) receptor stimulation with CGP-42112A delayed the onset of ANG II-induced constriction. PD-123319 alone (10(-5) M) showed no AT(1)-like action to constrict microperfused DVR or increase pericyte [Ca(2+)](i). We conclude that ANG II suppression of endothelial [Ca(2+)](i) and stimulation of pericyte [Ca(2+)](i) is mediated by AT(1) or AT(1)-like receptors. Furthermore, AT(2) receptor activation opposes ANG II-induced endothelial [Ca(2+)](i) suppression and abrogates ANG II-induced DVR vasoconstriction.
authors.affiliation: Division of Nephrology, University of Maryland School of Medicine, Baltimore 21201-1595, USA.
authors.forename: Kristie
authors.initials: K
authors.lastname: Rhinehart
authors.forename: Corey A
authors.initials: CA
authors.lastname: Handelsman
authors.forename: Erik P
authors.initials: EP
authors.lastname: Silldorff
authors.forename: Thomas L
authors.initials: TL
authors.lastname: Pallone
mesh_terms: D000804:Angiotensin II / Q000494:pharmacology; D057911:Angiotensin Receptor Antagonists; D000818:Animals; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D003593:Cytoplasm; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism*; D007093:Imidazoles / Q000494:pharmacology; D066298:In Vitro Techniques; D007679:Kidney Medulla / Q000098:blood supply*; D019808:Losartan / Q000494:pharmacology; D008345:Manganese / Q000493:pharmacokinetics; D008833:Microcirculation / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000098:blood supply; D020286:Pericytes / Q000187:drug effects / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D011945:Receptors, Angiotensin / Q000378:metabolism*; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D057911:Angiotensin Receptor Antagonists; D007093:Imidazoles; D011725:Pyridines; D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D011945:Receptors, Angiotensin; D014665:Vasodilator Agents; D000804:Angiotensin II; C073402:PD 123319; D008345:Manganese; D019808:Losartan; D002118:Calcium