NOS1-dependent negative feedback regulation of the epithelial sodium channel in the collecting duct.
With an increase in urine flow there is a significant increase in shear stress against the renal epithelium including the inner medullary collecting duct, resulting in an increase in nitric oxide (NO) production. The mechanisms of the shear stress-mediated increases in NO are undetermined. Previous studies found that shear stress increases epithelial sodium channel (ENaC) open probability and endothelin (ET)-1 production in an ENaC-dependent mechanism in the collecting duct (CD). Given that ET-1 stimulates NO production in the CD, we hypothesized that shear stress-induced NO production is downstream of shear stress-induced ENaC activation and ET-1 production in a negative feedback loop. We determined that nitric oxide synthase 1 (NOS1) and NOS3 contribute to shear stress-mediated NO production in the CD, that is attenuated by low doses of the ENaC inhibitors amiloride and benzamil. Moreover, ETB receptor blockade significantly blunted the shear stress-mediated NO production. We further elucidated whether mice lacking NOS1 in the collecting duct (CDNOS1KO) have an impaired renal ET-1 system in the CD. Although urinary ET-1 production and inner medullary ET receptor expression were similar between flox control and CDNOS1KO mice, acute ET-1 treatment significantly reduced ENaC open probability in CDs from flox mice but not CDNOS1KO mice compared with basal. Basal ENaC activity in CDs was similar between the genotypes. We conclude that during acute shear stress across the CD, ENaC acts in a negative feedback loop to stimulate NO production in an ETB/NOS1-dependent manner resulting in a decrease in ENaC open probability and promoting natriuresis.
Department of Medicine, Section of Cardio-Renal Physiology and Medicine, Division of Nephrology, University of Alabama at Birmingham, Birmingham, Alabama;
Kelly A
KA
Hyndman
Department of Physiology, University of Texas Health Science Center at San Antonio, San Antonio, Texas; and.
Vladislav
V
Bugaj
Department of Physiology, University of Texas Health Science Center at San Antonio, San Antonio, Texas; and.
Elena
E
Mironova
Department of Physiology, University of Texas Health Science Center at San Antonio, San Antonio, Texas; and.
James D
JD
Stockand
Department of Medicine, Section of Cardio-Renal Physiology and Medicine, Division of Nephrology, University of Alabama at Birmingham, Birmingham, Alabama; Department of Medicine, Georgia Regents University, Augusta, Georgia pollockj@uab.edu.
Jennifer S
JS
Pollock
D000584:Amiloride / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D019332:Endothelin-1 / Q000378:metabolism; D053503:Epithelial Sodium Channels / Q000378:metabolism*; D007685:Kidney Tubules, Collecting / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D009569:Nitric Oxide / Q000378:metabolism; D052248:Nitric Oxide Synthase Type I / Q000378:metabolism*; D044023:Receptor, Endothelin B; D012964:Sodium / Q000378:metabolism*
D019332:Endothelin-1; D053503:Epithelial Sodium Channels; D044023:Receptor, Endothelin B; C013407:benzamil; D009569:Nitric Oxide; D000584:Amiloride; D012964:Sodium; D052248:Nitric Oxide Synthase Type I; C496321:Nos1 protein, mouse
collecting duct; epithelial sodium channel; nitric oxide; nitric oxide synthase