High-salt diet increases sensitivity to NO and eNOS expression but not NO production in THALs.
L-Arginine inhibits thick ascending limb (THAL) NaCl absorption by activating endothelial NO synthase (eNOS) and increasing NO production. Inhibition of renal NO production combined with a high-salt diet produces hypertension, and the THAL has been implicated in salt-sensitive hypertension. We hypothesized that a high-salt diet enhances the inhibitory action of L-arginine on NaCl absorption by THALs because of increased eNOS expression and NO production. To test this, we used isolated THALs from rats on a normal-salt (NS) or high-salt diet (HS) for 7 to 10 days. L-Arginine (1 mmol/L) decreased chloride absorption by 56+/-10% in THALs from rats on a HS diet, but only 29+/-3% in THALs from rats on a NS diet. eNOS expression in isolated THALs from rats on a HS diet was increased by 3.9-fold compared with NS (P<0.03). However, L-arginine increased NO levels to the same extent in THALs from both groups, as measured with DAF-2 DA or a NO-sensitive electrode. To determine whether a HS diet increases the sensitivity of the THAL to NO, we tested the effects of the NO donor spermine NONOate on chloride absorption. In THALs from rats on a HS diet, 1 and 5 micromol/L spermine NONOate reduced chloride absorption by 35+/-5% and 58+/-6%, respectively. In contrast, these same concentrations of spermine NONOate reduced chloride absorption by 4+/-4% (P<0.03 versus HS diet) and 43+/-9% in THALs from rats on a NS diet. We conclude that a HS diet enhances the effect of NO in the THAL. L-Arginine-stimulated NO production was not enhanced by a HS diet, despite increased eNOS protein.
Ortiz
Pablo
P
Division of Hypertension and Vascular Research, Henry Ford Hospital, Detroit, MI 48202, USA. portiz1@hfhs.org
Stoos
Barbara A
BA
Hong
Nancy J
NJ
Boesch
Dianne M
DM
Plato
Craig F
CF
Garvin
Jeffrey L
JL
D000818:Animals; D001120:Arginine / Q000494:pharmacology; D002712:Chlorides / Q000378:metabolism; D046508:Culture Techniques; D004032:Diet; D017136:Ion Transport; D008138:Loop of Henle / Q000033:anatomy & histology / Q000201:enzymology* / Q000378:metabolism*; D008297:Male; D009569:Nitric Oxide / Q000096:biosynthesis*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D052250:Nitric Oxide Synthase Type III; D051381:Rats; D017207:Rats, Sprague-Dawley; D012965:Sodium Chloride / Q000494:pharmacology*
D002712:Chlorides; D020030:Nitric Oxide Donors; D009569:Nitric Oxide; D012965:Sodium Chloride; D001120:Arginine; D019001:Nitric Oxide Synthase; D052250:Nitric Oxide Synthase Type III; C496316:Nos3 protein, rat