Effects of sympathetic nerves and angiotensin II on renal sodium and water handling in rats with common bile duct ligature

Abstract

. Effects of sympathetic nerves and angiotensin II on renal sodium and water handling in rats with common bile duct ligature. Am J Physiol Renal Physiol 288: F1267-F1275, 2005. First published February 8, 2005 doi:10.1152/ajprenal.00069.2003.-We tested the hypothesis that angiotensin II is likely to be mandatory for the neurogenic sodium and volume retention in cirrhotic rats with common bile duct ligature (BDL) following an acute volume load. To assess the neural control of volume homeostasis, 21 days after common BDL rats underwent volume expansion (0.9% NaCL; 10% body wt over 30 min) to decrease renal sympathetic nerve activity. Untreated animals, rats with renal denervation or pretreated with a nonhypotensive dose of an angiotensin II type 1 receptor antagonist were studied. The renal renin-angiotensin system was assessed by immunohistochemistry and RT-PCR. Rats with BDL excreted only 71 Ϯ 4% of the administered volume load. In cirrhotic rats pretreated with an angiotensin II AT1 inhibitor or after renal denervation, these values ranged significantly higher from 98 to 103% (P Ͻ 0.05 for all comparisons). Renal sympathetic nerve activity decreases by volume expansion were impaired in BDL rats (P Ͻ 0.05) but unaffected by angiotensin II receptor inhibition. In kidneys of BDL animals, renin mRNA was increased, and immunohistochemistry revealed increased staining for peritubular angiotensin II. Renal denervation in BDL animals reduced renin expression within 5 days to control levels. In conclusion, the impaired excretion of an acute volume load in rats with liver cirrhosis is due to effects of an increased renal sympathetic nerve activity that are likely to be dependent on intrarenal angiotensin II and renin. We speculate that similar changes may contribute to long-term volume retention in liver cirrhosis. liver cirrhosis; nitric oxide; excretion SODIUM AND VOLUME RETENTION is a common problem in patients with liver cirrhosis (33, 34). Neurohumoral vasoconstrictors but also the production of a vasodilator like nitric oxide are considerably activated (16,21,22,27,29,31,42).Inhibition of the sympathetic nervous system (1, 35) or angiotensin II in patients (30, 38) or animal models (10,14,20) could improve sodium and water excretion transiently, although possible decreases in blood pressure or renal perfusion could eventually worsen volume homeostasis instead of improving it (1, 8, 9).We could demonstrate in rats that the effects of increased renal sympathetic nerve activity (RSNA) on renal sodium and water excretion could be inhibited by very low doses of an angiotensin II AT 1 receptor inhibitor not interfering with systemic angiotensin II effects or renal hemodynamics (39). These results suggested a tonic, indispensable influence of angiotensin II on the intrarenal effects of increased sympathetic drive. With respect to liver cirrhosis, these findings suggest the possibility that renal sodium and water handling could be improved by inducing a functional renal sympathetic inhibition with angiotensin II AT 1 rec...

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