GLOMERULAR PERMSELECTIVITY TO MACROMOLECULES IN REFLUX NEPHROPATHY - MICROALBUMINURIA DURING ACUTE HYPERFILTRATION DUE TO AMINO-ACID INFUSION

Reflux nephropathy is an important cause of chronic renal failure in c hildren. After the parenchymal scar, the progression is thought to be mediated by glomerular hypertension in remnant nephrons resulting in m odifications in permselectivity to macromolecules. Proteinuria correla tes with a progressive course. The glomerular permselectivity to macro molecules in basal conditions and after acute hemodynamic stress was i nvestigated in 28 children whose bilateral vesico-ureteric reflux (VUR ) had been previously surgically corrected (meanly 5.6 years before) a nd with normal creatinine clearance (CrCl). Bilateral renal scarring ( 0 to 8 scale for both kidneys) was 4.3 +/- 1.6. Albuminuria (UAE) was evaluated in basal conditions and under acute hyperfiltration induced by amino acid (Aa) infusion. After isotonic saline at 310 ml/hour/1.73 m2, 6 mg/kg/min of Aa were infused for 2 hrs. UAE was significantly h igher than controls in basal conditions (p <0.01), and further increas ed after Aa infusion (p <0.02). Microalbuminuria was detectable in 53. 5% of the children in basal conditions and in 64.3% after Aa. Also uri nary beta2 Microglobulin significantly increased at the end of the tes t (p <0.001). CrCl significantly increased at the first hour (p <0.05) . Children with severe renal parenchymal scarring had greater UAE (p < 0.01) and beta2M (P <0.02) values after provocative test than those wi th mild renal damage. In 8 children GFR and ERPF were measured by mean s of inulin and p-hippurate clearance respectively. The variations in UAE during Aa infusion were significantly correlated with GFR dynamics (p <0.05) while they were not in fluenced by ERPF modifications. In c hildren with initial RN and still normal CrCl a provocative test of hy perfiltration with Aa infusion induces a significant modification in p ermselectivity to macromolecules evidenced by microalbuminuria.