Faculty Collaboration Database

A novel amiloride-sensitive h+ transport pathway mediates enhanced superoxide production in thick ascending limb of salt-sensitive rats, not na+/h+ exchange. Hypertension 2009 Aug;54(2):248-54

Date

07/01/2009

Pubmed ID

19564541

Pubmed Central ID

PMC2771701

DOI

10.1161/HYPERTENSIONAHA.109.134692

Scopus ID

2-s2.0-68549085337 (requires institutional sign-in at Scopus site)   17 Citations

Abstract

It has been reported previously that H(+) efflux via the Na(+)/H(+) exchange stimulates NAD(P)H oxidase-dependent superoxide (O(2)(.-)) production in medullary thick ascending limb. We have demonstrated recently that N-methyl-amiloride-sensitive O(2)(.-) production is enhanced in the thick ascending limb of Dahl salt-sensitive (SS) rats, suggesting that H(+) efflux through Na(+)/H(+) exchangers may promote renal oxidative stress and the development of hypertension in these animals. In the current study we demonstrate, using selective and potent inhibitors, that inhibition of Na(+)/H(+) exchange does not mediate the ability of N-methyl-amiloride to inhibit thick ascending limb O(2)(.-) production. To determine the mechanism of action of N-methyl-amiloride, we examined H(+) efflux and O(2)(.-) production in SS and SS.13(BN) thick ascending limbs of prehypertensive, 0.4% NaCl-fed rats. Tissue strips containing the medullary thick ascending limb were isolated from male SS and salt-resistant consomic SS.13(BN) rats, loaded with either dihydroethedium or 2',7'-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein, acetoxymethyl ester, and imaged in a heated tissue bath. In Na(+)-replete media, activation of Na(+)/H(+) exchange using an NH(4)Cl prepulse did not stimulate thick ascending limb O(2)(.-) production. In Na(+)-free media containing BaCl(2) in which Na(+)/H(+) activity was inhibited, an NH(4)Cl prepulse stimulated O(2)(.-) production in medullary thick ascending limb renal tubular segments. This response was enhanced in medullary thick ascending limb of SS rats (slope Deltaethidium/Deltadihydroethedium=0.029+/-0.004) compared with SS.13(BN) rats (slope=0.010+/-0.004; P<0.04) and could be inhibited by N-methyl-amiloride (slope=0.005+/-0.002 and 0.006+/-0.002 for SS and SS.13(BN), respectively). We concluded that only H(+) efflux through a specific, as-yet-unidentified, amiloride-sensitive H(+) channel promotes O(2)(.-) production in the medullary thick ascending limb and that this channel is upregulated in SS rats.

Author List

O'Connor PM, Lu L, Liang M, Cowley AW Jr

Author

Allen W. Cowley Jr PhD Professor in the Physiology department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Amiloride
Animals
Disease Models, Animal
Hypertension
Kidney Tubules
Male
NADPH Oxidases
Nitric Oxide
Oxidative Stress
Probability
Random Allocation
Rats
Rats, Inbred Dahl
Sensitivity and Specificity
Signal Transduction
Sodium Chloride
Sodium-Hydrogen Exchangers
Superoxides