TY - JOUR
T1 - Production of superoxide through NADH oxidase in thick ascending limb of Henle's loop in rat kidney
AU - Li, Ningjun
AU - Yi, Fu Xian
AU - Spurrier, Jamie L.
AU - Bobrowitz, Carol A.
AU - Zou, Ai Ping
PY - 2002
Y1 - 2002
N2 - We recently reported that NADH oxidase is one of the major enzymes responsible for superoxide (O-2·) production in the rat kidney. However, the functional significance of NADH oxidase-mediated O-2· production and the mechanisms regulating this enzyme activity are poorly understood. Using fluorescence microscopic imaging analysis, the present study demonstrated that thick ascending limbs of Henle's loop (TALHs) exhibited red fluorescence when incubated with dihydroethidium (DHE), suggesting that O-2· is produced in this tubular segment. Compared with other nephron segments, TALHs from both renal cortex and medulla showed the highest fluorescence intensity. By incubating cortical TALHs (cTALHs) with the substrates of NADH oxidase, xanthine oxidase, nitric oxide synthase, arachidonic acid-metabolizing enzymes, and intramitochondrial oxidases, NADH oxidase was found to be one of the most important enzymes for O-2· production in this tubular segment. The NADH oxidase inhibitor diphenyleneiodonium (DPI; 100 μM) completely blocked NADH-induced O-2· production in cTALHs. Exposure of cTALHs to low Po2 (5-10 Torr) significantly increased O-2 production regardless of the absence or presence of NADH. Furthermore, angiotensin II (100 nM) increased NADH oxidase activity by 32%, which was completely blocked by DPI. These results suggest that NADH oxidase is a major enzyme responsible for O-2· production in the TALHs and that the production of O-2· via NADH oxidase may be regulated by renal tissue oxygenation and circulating hormones.
AB - We recently reported that NADH oxidase is one of the major enzymes responsible for superoxide (O-2·) production in the rat kidney. However, the functional significance of NADH oxidase-mediated O-2· production and the mechanisms regulating this enzyme activity are poorly understood. Using fluorescence microscopic imaging analysis, the present study demonstrated that thick ascending limbs of Henle's loop (TALHs) exhibited red fluorescence when incubated with dihydroethidium (DHE), suggesting that O-2· is produced in this tubular segment. Compared with other nephron segments, TALHs from both renal cortex and medulla showed the highest fluorescence intensity. By incubating cortical TALHs (cTALHs) with the substrates of NADH oxidase, xanthine oxidase, nitric oxide synthase, arachidonic acid-metabolizing enzymes, and intramitochondrial oxidases, NADH oxidase was found to be one of the most important enzymes for O-2· production in this tubular segment. The NADH oxidase inhibitor diphenyleneiodonium (DPI; 100 μM) completely blocked NADH-induced O-2· production in cTALHs. Exposure of cTALHs to low Po2 (5-10 Torr) significantly increased O-2 production regardless of the absence or presence of NADH. Furthermore, angiotensin II (100 nM) increased NADH oxidase activity by 32%, which was completely blocked by DPI. These results suggest that NADH oxidase is a major enzyme responsible for O-2· production in the TALHs and that the production of O-2· via NADH oxidase may be regulated by renal tissue oxygenation and circulating hormones.
KW - Hypoxia
KW - Oxidative stress
KW - Reactive oxygen species
KW - Redox signaling
KW - Renal tubule
UR - http://www.scopus.com/inward/record.url?scp=0036088542&partnerID=8YFLogxK
U2 - 10.1152/ajprenal.00218.2001
DO - 10.1152/ajprenal.00218.2001
M3 - Article
C2 - 11997328
AN - SCOPUS:0036088542
SN - 1931-857X
VL - 282
SP - F1111-F1119
JO - American Journal of Physiology - Renal Physiology
JF - American Journal of Physiology - Renal Physiology
IS - 6 51-6
ER -