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.jpg): Failed to open stream: No such file or directory in C:\Inetpub\vhosts\kidney.de\httpdocs\pget.php on line 117 Am+J+Physiol+Renal+Physiol
2016 ; 310
(8
): F748-F754
Nephropedia Template TP
Am J Physiol Renal Physiol
2016[Apr]; 310
(8
): F748-F754
PMID26887831
show ga
In thick ascending limbs (THALs), nitric oxide (NO) decreases NaCl reabsorption
via cGMP-mediated inhibition of Na-K-2Cl cotransporter (NKCC2). In angiotensin
(ANG II)-induced hypertension, endothelin-1 (ET-1)-induced NO production by THALs
is impaired. However, whether this alters NO's natriuretic effects and the
mechanisms involved are unknown. In other cell types, ANG II augments
phosphodiesterase 5 (PDE5)-mediated cGMP degradation. We hypothesized that
NO-mediated inhibition of NKCC2 activity and stimulation of cGMP synthesis are
blunted via PDE5 in ANG II-induced hypertension. Sprague-Dawley rats were infused
with vehicle or ANG II (200 ng·kg(-1)·min(-1)) for 5 days. ET-1 reduced NKCC2
activity by 38 ± 13% (P < 0.05) in THALs from vehicle-treated rats but not from
ANG II-hypertensive rats (?: -9 ± 13%). A NO donor yielded similar results as
ET-1. In contrast, dibutyryl-cGMP significantly decreased NKCC2 activity in both
vehicle-treated and ANG II-hypertensive rats (control: ?-44 ± 15% vs. ANG II:
?-41 ± 10%). NO increased cGMP by 2.08 ± 0.36 fmol/?g protein in THALs from
vehicle-treated rats but only 1.06 ± 0.25 fmol/?g protein in ANG II-hypertensive
rats (P < 0.04). Vardenafil (25 nM), a PDE5 inhibitor, restored NO's ability to
inhibit NKCC2 activity in THALs from ANG II-hypertensive rats (?: -60 ± 9%, P <
0.003). Similarly, NO's stimulation of cGMP was also restored by vardenafil
(vehicle-treated: 1.89 ± 0.71 vs. ANG II-hypertensive: 2.02 ± 0.32 fmol/?g
protein). PDE5 expression did not differ between vehicle-treated and ANG
II-hypertensive rats. We conclude that NO-induced inhibition of NKCC2 and
increases in cGMP are blunted in ANG II-hypertensive rats due to PDE5 activation.
Defects in the response of THALs to NO may enhance NaCl retention in ANG
II-induced hypertension.