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Purpose: The pathogenesis of kidney stones remains elusive. There is some evidence that hyperoxaluria may effect vascular endothelium and many studies link renal stones to atherosclerosis. Also, renal vascular endothelial cells regulate proximal tubular epithelial cell function. We determined the effect of hyperoxaluria on plasma and tissue levels of asymmetrical dimethylarginine. The secondary aim was to determine the effect of verapamil on asymmetrical dimethylarginine., Materials and Methods: A total of 42 Sprague-Dawley rats were included in the study. In groups 1A, 1B and 1C hyperoxaluria was induced with ethylene glycol for 2 weeks. Groups 2A, 2B and 2C received ethylene glycol for 14 days and verapamil for 28 days. Control group 3 received no specific medication but distilled water. Blood samples were obtained at 24 hours and at study end, and kidney samples were obtained at 24 hours, and 7 and 28 days for histopathological evaluation., Results: Plasma asymmetrical dimethylarginine increased early in the hyperoxaluric group (p = 0.0002). The effect was retained at the end of the study period (p = 0.01). There was no increase in asymmetrical dimethylarginine in the verapamil group on short-term and long-term followup. Hyperoxaluria induced a significantly dense staining pattern in renal tissue asymmetrical dimethylarginine vs controls (p = 0.01). Asymmetrical dimethylarginine staining did not differ in the control and verapamil groups., Conclusions: Increased systemic and local tissue asymmetrical dimethylarginine may help explain the pathogenetic mechanisms of hyperoxaluria induced disorders such as nephrolithiasis and atherosclerosis., (Copyright 2010 American Urological Association. Published by Elsevier Inc. All rights reserved.)