Neonatal renal hemodynamics are characterized by a specific pattern of reactivity to various mediators, including nitric oxide (NO). Knowlegde on the role of NO in renal hemodynamics often relies on the interpretation of the effects of NO-synthase (NOS) inhibitors and/or NOS substrates L-arg analogues on renal vascular function. The aim of this study was to characterize the effects on neonatal renal hemodynamics in the rabbit of NG-nitro L-arginine methyl ester (L-NAME) and NG-monomethyl-L-arginine (L-NMMA), as NOS inhibitors, and of L-arg and benzoyl-arginine ethylester (BAEE), as NOS substrates.

An open-circuit, constant flow, isolated perfused kidney (IPK) model was used. Kidneys of 7 day old (N=20) and of adult rabbits (N=20) were perfused in vitro with a modified, heated and oxygenated Krebs-Enselheit medium, in control conditions, or in the presence of 10-4 M L-NAME, L-NMMA, L-NAME + L-arg or L-NAME + BAEE. Perfusion pressure was measured at constant flow using a double-lumen catheter and was considered to reflect RVR.

Results are given in the table and are expressed in ml/min/mm Hg, as means ± SEM (*:p<0.05 compared to controls).

Table 1
Full size table

These results evidence specific effects of the tested L-arg analogues on the neonatal rabbit renal vasculature. L-NAME is a more potent NOS inhibitor than L-NMMA, and BAEE allows a better reversion of the NOS inhibition in the newborn animal. Evidence on the biologic roles of NO in the neonatal kidney may depend on the NOS inhibitor/substrate which are used in the experiments.