Endothelium-derived relaxing factor modulates renal interstitial cyclic GMP.

The arterial vasodilator activity of endothelium-derived relaxing factor (EDRF) is mediated by activation of the soluble form of guanylate cyclase, causing increased levels of guanosine-3',5'-cyclic monophosphate (cGMP). Because of its extreme lability, the actions of EDRF are local. The ability to monitor changes in renal interstitial fluid cGMP would be of great advantage in clarification of local mechanisms controlling renal function. Utilizing a renal interstitial microdialysis technique, we investigated changes in renal interstitial and urinary cGMP in response to right intrarenal arterial administration of the EDRF inhibitor, NG-monomethyl-L-arginine (L-NMMA), in anesthetized dogs (n = 5) in metabolic balance at a sodium intake of 40 mEq/day. Urine was collected directly from the right and left ureter. L-NMMA at 20-60 micrograms/kg/min significantly decreased right renal interstitial and right urinary cGMP levels (p < 0.01) without changing left renal interstitial and urinary cGMP levels (p < 0.01). L-NMMA at 100 micrograms/kg/min decreased both right and left renal interstitial and urinary cGMP levels (p < 0.01). These data demonstrate the ability to monitor renal interstitial cGMP in vivo. There was a dose-dependent decrease in renal interstitial and urinary cGMP in response to intrarenal EDRF inhibition. Additionally, they suggest that EDRF acts as a renal paracrine substance through the modulation of renal interstitial cGMP.