Objective: PDE5 inhibitors represent the first line therapy for treatment of ED.However,diabetic patients have poorer response compared with normal patients.The aim of this study was to determine whether taurine,a sulfurcontaining amino acid,affects diabetic erectile dysfunction.Methods: Type 1 diabetes mellitus was induced in male rats by streptozotocin(60 mg/kg,intraperitoneally).After 12 weeks,apomorphine test was conducted to confirm diabetic erectile dysfunction(DED).Only DED rats were administered taurine(400 mg/kg/day,intraperitoneally)or vehicle,for 4 weeks.Age-matched control,nondiabetic,rats were treated with saline intraperitoneally for 4 weeks.At week 16,after a 2-day washout,erectile function was evaluated.Peniles were harvested for Western blot analysis of RhoA,ROCK-1,ROCK-2,eNOS,nNOS,NADPH oxidase subunit gp91 phox.Results: Erectile function was significantly destroyed in diabetic rats compared with nondiabetic rats and was ameliorated in diabetic rats treated with taurine.In diabetic rats,RhoA,ROCK-1,ROCK-2 and gp91phox protein expressions were increased,whereas eNOS and nNOS expressions were decreased compared with nondiabetic rats,and both were reversed in diabetic rats treated with taurine.Conclusions: Taurine improves erectile function in diabetic rats probably by inhibiting RhoA/Rock and activating NOS/NO signaling pathways.This may provide a potential new therapy for diabetic ED.