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 importance of bradykinin and nitric oxide (NO) in mediating renal responses to altered 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 technique 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 bradykinin B2 receptor antagonist icatibant or the NO synthase inhibitor nitro-L-arginine methyl ester (L-NAME). Urine sodium excretion was monitored simultaneously 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 both 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 significantly 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 RIF cGMP in Dahl-SR and Dahl-SS rats on low sodium diet, but reduced RIF cGMP 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 intake between Dahl-SR and Dahl-SS rats.