title: Angiotensin II-mediated hypertension impairs nitric oxide-induced NKCC2 inhibition in thick ascending limbs.
abstract: 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 (Δ: -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: Δ-44 ± 15% vs.
  
  
  
  Δ-41 ± 10%). NO increased cGMP by 2.08 ± 0.36 fmol/μg protein in THALs from vehicle-treated rats but only 1.06 ± 0.25 fmol/μg 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 (Δ: -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/μg 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.
authors.affiliation: Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Health System, Detroit, Michigan; vramseye@med.wayne.edu.|Department of Physiology, School of Medicine, Wayne State University, Detroit, Michigan; and.
authors.forename: Vanesa D
authors.initials: VD
authors.lastname: Ramseyer
authors.affiliation: Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Health System, Detroit, Michigan.|Department of Physiology, School of Medicine, Wayne State University, Detroit, Michigan; and.
authors.forename: Pablo A
authors.initials: PA
authors.lastname: Ortiz
authors.affiliation: Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Health System, Detroit, Michigan.
authors.forename: Oscar A
authors.initials: OA
authors.lastname: Carretero
authors.affiliation: Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Health System, Detroit, Michigan.|Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, Ohio.
authors.forename: Jeffrey L
authors.initials: JL
authors.lastname: Garvin
mesh_terms: D000804:Angiotensin II; D000818:Animals; D003563:Cyclic CMP / Q000031:analogs & derivatives / Q000494:pharmacology; D006152:Cyclic GMP / Q000378:metabolism; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5 / Q000378:metabolism; D019332:Endothelin-1 / Q000494:pharmacology*; D006973:Hypertension / Q000139:chemically induced / Q000378:metabolism*; D008138:Loop of Henle / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D058986:Phosphodiesterase 5 Inhibitors / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D064466:Solute Carrier Family 12, Member 1 / Q000378:metabolism*; D000069058:Vardenafil Dihydrochloride / Q000494:pharmacology
chemical_list: D019332:Endothelin-1; D020030:Nitric Oxide Donors; D058986:Phosphodiesterase 5 Inhibitors; D064466:Solute Carrier Family 12, Member 1; D000804:Angiotensin II; D009569:Nitric Oxide; D003563:Cyclic CMP; D000069058:Vardenafil Dihydrochloride; C053441:dibutyryl cyclic-3',5'-cytidine monophosphate; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5; C517384:Pde5a protein, rat; D006152:Cyclic GMP
keywords: cGMP; endothelin-1; kidney; phosphodiesterase 5; sodium transport