Effect of castration and finasteride on urinary oxalate excretion in male rats.

We investigated the effects of castration and finasteride administration on urinary oxalate (Ox) excretion in a rat ethylene glycol (EG) model of urolithiasis. Male adult SD rats were divided into six groups. Group 1 were normal, untreated rats. The other five groups, all treated with 0.75% EG for 4 weeks; were as follows: group 2, non-castrated (intact) rats; group 3, castrated rats; group 4, castrated rats with a 4-cm testosterone implant; group 5, intact rats treated with high-dose finasteride (7.5 mg%); and group 6, intact rats treated with low-dose finasteride (0.75 mg%). Urinary Ox excretion increased 12.8-fold after 4 weeks of EG treatment (group 2 vs group 1). Both castration (group 3) and finasteride administration (groups 5 and 6) significantly decreased urinary Ox excretion compared with intact rats (group 2). We conclude that dihydrotestosterone is partially responsible for the exaggerated hyperoxaluria observed in the rat EG model of urolithiasis.