Effect of Trenbolone enanthate on protein degradation in levator ani/bulbocavernosus (LABC) muscle in orchiectomized rats

Trenbolone (TREN), a potent testosterone analog, does not undergo 5[alpha]‐reduction to the more potent metabolite dihydrotestosterone (DHT) and may produce androgenic effects without DHT‐mediated adverse effects. The purpose of this study was to investigate the mechanism underlying the trenbolone – induced augmentation of LABC muscle mass in orchiectomized (ORX) rats. Forty, 10 month old male F344/Brown Norway rats were randomized into SHAM, ORX, ORX+TE, and ORX+TREN groups. Following surgery, animals recovered for 1 week and then were treated with vehicle, TE, or TREN by weekly i.m. injection. 5 weeks of TE administration nearly doubled prostate mass, while TREN resulted in a nonsigificant reduction in prostate mass, compared with SHAMs. ORX induced a significant 2‐fold elevation atrogin‐1 and a 3‐fold elevation in Muscle RING Finger‐1 mRNA expression, effects which were completely abolished by TE and TREN. Interestingly, TREN induced a greater decrease in atrogin‐1 gene expression compared to TE. These data suggest that TREN may prevent muscle loss after ORX through inhibiting master genes that regulate skeletal muscle atrophy. This work was supported by VA Merit Award to SEB and a VA Career Development Award‐2 to JFY.