Cyclic GMP release and vasodilatation induced by EDRF and atrial natriuretic factor in the isolated perfused kidney of the rat

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Abstract
1 Guanosine 3′:5′-cyclic monophosphate (cyclic GMP) release and vascular tone was measured in the isolated kidney of the rat perfused at constant flow with Krebs-Henseleit solution. The effects of 3 vasodilators, acetylcholine (ACh), atrial natriuretic factor (ANF) and sodium nitroprusside (SNP) on the renal release of cyclic GMP and vascular tone were examined. The ability of the endothelial-derived relaxing factor (EDRF) inhibitors, haemoglobin and gossypol, to modify vasodilatation and vasodilator-induced changes in cyclic GMP releases from the kidney was also investigated. 2 Renal cyclic GMP release was elevated 8 fold by ANF (0.01 μm), 5 fold by SNP (1 μm) and 3 fold by ACh (0.3 μm). 3 For ACh, both the increase in renal cyclic GMP release and the vasodilatation were reduced by the EDRF inhibitors, haemoglobin (1 μm) and gossypol (15 μm). For SNP, neither the increase in renal cyclic GMP release nor vasodilatation were inhibited by gossypol (15 μm). 4 For ANF, neither the increase in cyclic GMP release from the kidney nor its vasodilator activity were affected by haemoglobin (1 μm). 5 EDRF inhibitors reduced the basal release of cyclic GMP from 0.32 ± 0.06 pmol min−1 to 0.18 ± 0.03 pmol min−1, gossypol being more effective than haemoglobin. 6 The results are consistent with the ability of ACh to induce EDRF-mediated vasodilatation in the isolated perfused kidney of the rat. Basal EDRF release appears to contribute approximately 50% to the basal release of cyclic GMP from this preparation. The renal vasodilator action of ANF however, is independent of EDRF, although the renal vascular endothelium cannot be discounted as a site at which ANF stimulates cyclic GMP production.