title: Enhanced amiloride-sensitive superoxide production in renal medullary thick ascending limb of Dahl salt-sensitive rats.
abstract: The aims of the present study were to determine whether superoxide (O(2)(-)) production is enhanced in medullary thick ascending limb (mTAL) of Dahl salt-sensitive (SS) rats compared with a salt-resistant consomic control strain (SS.13(BN)) and to elucidate the cellular pathways responsible for augmented O(2)(-) production. Studies were carried out in 7- to 10-wk-old male SS and SS.13(BN) rats fed either a 0.4% NaCl diet or a 4.0% NaCl diet for 3 days before tissue harvest. Tissue strips containing mTAL were isolated from the left kidney, loaded with the O(2)(-)-sensitive fluorescent dye dihydroethidium, superfused with modified Hanks' solution, and imaged at x60 magnification on a heated microscope stage. O(2)(-) production was stimulated in mTAL by incrementing superfusate NaCl concentration from 154 to 254 to 500 mM. O(2)(-) production was enhanced in mTAL of SS rats compared with SS.13(BN) rats in response to incrementing bath NaCl. Addition of N-methyl-amiloride (100 muM) or inhibition of NAD(P)H oxidase reduced O(2)(-) production in SS mTAL to levels observed in SS.13(BN) rats. Both amiloride- and ouabain-sensitive pathways of O(2)(-) production were elevated following 3 days of high (4.0%) NaCl feeding in mTAL of SS and SS.13(BN) rats. We conclude that mTAL from SS rats exhibit enhanced amiloride-sensitive O(2)(-) production. The amiloride-sensitive O(2)(-) response in mTAL is independent of active Na(+) transport and appears to be mediated by NAD(P)H oxidase. Amiloride-sensitive O(2)(-) production is likely to contribute to augmented outer medullary O(2)(-) production observed in SS rats during both normal and high NaCl diets.
authors.affiliation: Department of Physiology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53202, USA. poconnor@mcw.edu
authors.forename: Paul M
authors.initials: PM
authors.lastname: O'Connor
authors.forename: Limin
authors.initials: L
authors.lastname: Lu
authors.forename: Carlos
authors.initials: C
authors.lastname: Schreck
authors.forename: Allen W
authors.initials: AW
authors.lastname: Cowley
mesh_terms: D000584:Amiloride / Q000494:pharmacology*; D000818:Animals; D048429:Cell Size; D004195:Disease Models, Animal; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D045604:Extracellular Fluid / Q000378:metabolism; D006973:Hypertension / Q000139:chemically induced; D066298:In Vitro Techniques; D007679:Kidney Medulla / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D019255:NADPH Oxidases / Q000037:antagonists & inhibitors; D009994:Osmolar Concentration; D018384:Oxidative Stress; D051381:Rats; D020303:Rats, Inbred Dahl; D012964:Sodium / Q000378:metabolism; D026941:Sodium Channel Blockers / Q000494:pharmacology*; D012965:Sodium Chloride / Q000494:pharmacology; D012982:Sodium, Dietary / Q000009:adverse effects; D013481:Superoxides / Q000378:metabolism*; D019459:Urothelium / Q000187:drug effects / Q000378:metabolism
chemical_list: D026941:Sodium Channel Blockers; D012982:Sodium, Dietary; D013481:Superoxides; D012965:Sodium Chloride; D000584:Amiloride; D012964:Sodium; D019255:NADPH Oxidases