Renal cyclic 3 ',5 '-guanosine monophosphate and sodium excretion in Dahl salt-resistant and Dahl salt-sensitive rats: comparison of the roles of bradykinin and nitric oxide

Objective The purpose of this study was to determine the relative importanc e of bradykinin and nitric oxide (NO) in mediating renal responses to alter ed sodium intake in Dahl salt-resistant (Dahl-SR) and salt-sensitive (Dahl- SS) rats. Design and methods Dahl-SR and Dahl-SS rats consumed a diet containing 0.15 % (low) or 4.0% (high) sodium chloride for 10 days. A microdialysis techniq ue was then used to measure renal cortical interstitial fluid (RIF) cyclic 3',5'-guanosine monophosphate (cGMP) production in anesthetized rats, under baseline conditions and during acute cortical infusion of either the brady kinin B-2 receptor antagonist icatibant or the NO synthase inhibitor nitro- L-arginine methyl ester (L-NAME). Urine sodium excretion was monitored simu ltaneously by ureter cannulation. Results Baseline sodium excretion was similar in the two types of rats, but RIF cGMP was significantly elevated in Dahl-SR compared to Dahl-SS rats on both low and high sodium diets. Icatibant infusion significantly reduced b oth RIF cGMP and sodium excretion in Dahl-SR rats during low sodium intake, but had no effect in Dahl-SS rats on either diet L-NAME infusion significa ntly reduced sodium excretion in Dahl-SR and Dahl-SS rats, during both low and high sodium intake. L-NAME infusion caused a significant reduction in R IF cGMP in Dahl-SR and Dahl-SS rats on low sodium diet, but reduced RIF cGM P only in Dahl-SR rats on high sodium diet. Conclusion These data suggest a potential role for cortical bradykinin, but not NO, in mediating the differences in the renal response to low sodium i ntake between Dahl-SR and Dahl-SS rats. J Hypertens 18:1491-1496 (C) 2000 L ippincott Williams & Wilkins.