Angiotensin II-induced hypertension blunts thick ascending limb NO production by reducing NO synthase 3 expression and enhancing threonine 495 phosphorylation.
Thick ascending limbs reabsorb 30% of the filtered NaCl load. Nitric oxide (NO) produced by NO synthase 3 (NOS3) inhibits NaCl transport by this segment. In contrast, chronic angiotensin II (ANG II) infusion increases net thick ascending limb transport. NOS3 activity is regulated by changes in expression and phosphorylation at threonine 495 (T495) and serine 1177 (S1177), inhibitory and stimulatory sites, respectively. We hypothesized that NO production by thick ascending limbs is impaired by chronic ANG II infusion, due to reduced NOS3 expression, increased phosphorylation of T495, and decreased phosphorylation of S1177. Rats were infused with 200 ng·kg(-1)·min(-1) ANG II or vehicle for 1 and 5 days. ANG II infusion for 5 days decreased NOS3 expression by 40 ± 12% (P < 0.007; n = 6) and increased T495 phosphorylation by 147 ± 26% (P < 0.008; n = 6). One-day ANG II infusion had no significant effect. NO production in response to endothelin-1 was blunted in thick ascending limbs from ANG II-infused animals [ANG II -0.01 ± 0.06 arbitrary fluorescence units (AFU)/min vs. 0.17 ± 0.02 AFU/min in controls; P < 0.01]. This was not due to reduced endothelin-1 receptor expression. Phosphatidylinositol 3,4,5-triphosphate (PIP3)-induced NO production was also reduced in ANG II-infused rats (ANG II -0.07 ± 0.06 vs. 0.13 ± 0.04 AFU/min in controls; P < 0.03), and this correlated with an impaired ability of PIP3 to increase S1177 phosphorylation. We conclude that in ANG II-induced hypertension NO production by thick ascending limbs is impaired due to decreased NOS3 expression and altered phosphorylation.
Hypertension and Vascular Research, Department of Internal Medicine, Henry Ford Hospital, Detroit, Michigan; Center for Molecular Medicine and Genetics, School of Medicine, Wayne State University, Detroit, Michigan;
Vanesa D
VD
Ramseyer
Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, Ohio; and Universidad de Buenos Aires, Facultad de Farmacia y Bioquímica, Ciudad Autónoma de Buenos Aires, Argentina.
Agustin
A
Gonzalez-Vicente
Hypertension and Vascular Research, Department of Internal Medicine, Henry Ford Hospital, Detroit, Michigan;
Oscar A
OA
Carretero
Hypertension and Vascular Research, Department of Internal Medicine, Henry Ford Hospital, Detroit, Michigan; Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, Ohio; and jeffrey.garvin@case.edu.
Jeffrey L
JL
Garvin
D000804:Angiotensin II / Q000378:metabolism*; D000818:Animals; D008138:Loop of Henle / Q000378:metabolism*; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism*; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D017207:Rats, Sprague-Dawley
D000804:Angiotensin II; D009569:Nitric Oxide; D052250:Nitric Oxide Synthase Type III; C496316:Nos3 protein, rat; D011493:Protein Kinase C
blood pressure; kidney; renal medulla; salt sensitivity