Angiotensin II-NAD(P)H oxidase-stimulated superoxide modifies tubulovascular nitric oxide cross-talk in renal outer medulla.
The source of superoxide (O2*-) production and cell-to-cell interactions of O2*- and nitric oxide (NO) in response to angiotensin II (AngII) were studied by fluorescence microscopic techniques to image rat renal outer medullary microtissue strips. Changes in intracellular O2*- were determined by dihydroethidium-ethidium ratios, and NO was determined with 4,5-diaminofluorescein diacetate. AngII (1 micromol/L) significantly increased O2*- in the isolated, medullary thick ascending limb (mTAL). These responses were inhibited by the superoxide dismutase mimetic 4-hydroxytetramethylpiperidine-1-oxyl (TEMPOL) and by the NAD(P)H oxidase inhibitors diphenylene iodonium and apocynin. AngII did not increase O2*- in either pericytes of isolated, intact vasa recta (VR) or pericytes of VR with a disrupted endothelium, even when surrounded by mTAL. However, AngII did increase O2*- when the tissue strips were preincubated with the NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (carboxy-PTIO), indicating that cross-talk of O2*- from mTAL to the VR occurred but was normally inhibited by NO. Also, tissue O2*- reduction by TEMPOL increased the diffusion of NO from mTAL to the pericytes, indicating that cross-talk of NO from the mTAL to the VR is also inhibited by O2*-. We conclude that AngII stimulates O2*- production in mTAL via the NAD(P)H oxidase pathway and that interactions of O2*- and NO ultimately determine the effectiveness of in situ free-radical cross-talk between the mTAL and the VR.
Mori
Takefumi
T
Department of Physiology, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
Cowley
Allen W
AW
D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D046508:Culture Techniques; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D007679:Kidney Medulla / Q000098:blood supply* / Q000166:cytology / Q000378:metabolism*; D007686:Kidney Tubules, Distal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism*; D019255:NADPH Oxidases; D009569:Nitric Oxide / Q000378:metabolism*; D019899:Paracrine Communication; D020286:Pericytes / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013481:Superoxides / Q000378:metabolism*
D013481:Superoxides; D000804:Angiotensin II; D009569:Nitric Oxide; D009247:NADH, NADPH Oxidoreductases; D019255:NADPH Oxidases