Urodilatin, not nitroprusside, combined with dopamine reverses ischemic acute renal failure

The present study was undertaken to: (a) clarify the comparative renal potency of bolus injection of the natriuretic peptides urodilatin and ANF99-126 in the rat; (b) establish whether or not intravenous (i.v.) infusion of urodilatin (200 ng/min) combined with dopamine (UD) to maintain mean arterial pressure could improve GFR or renal histology in established experimental ischemic acute renal failure (ARF) induced by 30 minutes of bilateral renal artery clamping; (c) assess comparative efficacies of nitroprusside, an activator of soluble guanylate cyclase, combined with dopamine (ND) or control infusions of dopamine alone (DA), under equivalent conditions; and (d) determine effects of intra-renal arterial infusions of the stable cGMP analogue dibutyryl-cGMP immediately after renal artery clamping (RAC). After initial dose finding studies, i.v. infusion of UD 24 hours after 30 minutes of RAC improved GFR over five hours from 0.24 +/- 0.04 to 1.0 +/- 0.16 ml/min in association with a threefold rise in plasma cGMP and a 13-fold increase in urinary cGMP excretion. Plasma creatinine dropped by 41% from 230 +/- 16 to 135 +/- 18 microM/liter and was still reduced 24 hours later with values averaging 106 +/- 14 compared to 274 +/- 53 microM/liter in non-treated animals. During infusion, UV and FENa+ increased from 1.4 +/- 0.2 to 8.3 ml/min, and from 2.9 +/- 0.5 to maximum values of 15.8 +/- 2.4%. ND or DA alone were less effective, increasing GFR only to 14 and 20%, respectively, of normal values, but improvements were not sustained; in contrast to UD, ND did not alter plasma or urinary cGMP. In addition, DBcGMP was ineffective in improving GFR during early ARF. Histologically UD, but not ND, markedly reduced the incidence of granular casts, tubular desquamation and tubular necrosis in cortical areas and increased the incidence of medullary mitoses.