Background: Oral supplementation of L-arginine (L-arg) is found to be beneficial in many kidney disorders. We determined whether L-arg supplementation safeguards the renal epithelial cell damage induced by hyperoxaluria with excretion of urinary marker enzymes and lithogenic salts with special reference to Tamm-Horsfall glycoprotein (THP). Methods: Hyperoxaluria was induced by 0.75% ethylene glycol (EG) in drinking water. L-Arg was co-supplemented at the dose of 1.25 g/kg b.w. orally for 28 days. At the end of experimental period, 24-h urine samples were collected in all the experimental groups. Isolation and purification of THP was carried in rat urine and were subjected to spectrophotometric crystallization assay and calcium-14C-oxalate binding studies. Determination of the lithogenic risk factors like calcium, oxalate, phosphorus, citrate, and marker enzymes such as lactate dehydrogenase (LDH) and γ-glutamyltransferase (γ-GT) were carried out in the collected urine sample. Results: Urinary excretion of calcium and oxalate was significantly increased in EG-treated rats. In L-arg supplemented hyperoxaluric rats, these concentrations were significantly (p < 0.001) decreased when compared to that of hyperoxaluric rats, and were moderately elevated from that of control rats. The activities of urinary marker enzymes, both LDH and γ-GT were 2-fold increased in EG-treated rats, when compared to control rats, but these values were maintained near normal in L-arg supplemented EG-treated rats. Citrate excretion was enhanced in the L-arg co-supplemented hyperoxaluric rats. In spectrophotometric crystallization assay system, L-arg supplemented rat THP showed inhibition in nucleation and aggregation phases, whereas EG-treated rat THP showed promotion of both calcium oxalate nucleation and aggregation phases. In calcium-14C-oxalate binding assay, THP derived from hyperoxaluric rats exhibited 2-fold increase (p < 0.001) in the Ca* Ox binding when compared to control and L-arg supplemented animals. Conclusions: L-Arg could act as a potent antilithic agent, by increasing the level of citrate in the hyperoxaluria-induced rats and decreasing calcium oxalate binding to the THP. L-Arg also effectively prevents the deposition of calcium oxalate crystals by curtailing the renal epithelial damage and protein oxidation as evidenced by the normal activities of urinary marker enzymes in L-arg supplemented hyperoxaluric rats. © 2005 Elsevier B.V. All rights reserved.