Activation of Intrarenal Renin-Angiotensin System during Metabolic Acidosis

Background: Chronic metabolic acidosis is a common metabolic disturbance and its clinical impact can be severe and extensive. The role and the change of the intrarenal renin-angiotensin system (RAS) during metabolic acidosis are uncertain, and whether acidosis can evoke inflammation remains unclear. Methods: Male Sprague-Dawley rats were fed with water containing 0.14 M NH 4 Cl to induce metabolic acidosis for 1 and 8 weeks, respectively. They were compared with animals fed with deionized water (control) and equimolar sodium chloride water (NaCl). Gene expression analysis of RAS components included renin, renin/prorenin receptor, angiotensinogen, angiotensin-converting enzyme (ACE), and angiotensin II type 1 and 2 receptors (AT1R and AT2R). Histological examination was also performed to detect morphological change. Results: Acidosis was found in 1-week NH 4 Cl-treated rats but not in the 8-week group. More than twofold proteinuria and a significant decline of glomerular filtration rate (GFR) were observed in acid-loaded rats. Compared to the control and NaCl groups, angiotensinogen, ACE, AT1R and AT2R were significantly increased in the 1-week acidosis group (all p < 0.05). Sustained increase of AT1R expression was found as NH 4 Cl was continued for 8 weeks. There was no significant change in transforming growth factor-β and nuclear factor-ĸB. The architecture of tubular epithelial cells was affected during our experiment. Conclusion: Metabolic acidosis induced proteinuria and decline of GFR in association with activation of intrarenal RAS.