ABSTRACT
<p><b>OBJECTIVE</b>To investigate whether 5alpha-reductase inhibitor and dihydrotestosterone (DHT) play a role in spermatogenesis in male rats.</p><p><b>METHODS</b>Thirty-two male rats were divided into 4 groups (Groups C, T, F and FT). Group C received plant oil injection and oral starch perfusion, Group T testosterone undecanoate (TU, 20 mg/kg) injection and oral starch perfusion, Group F plant oil injection and oral Finasteride perfusion, and Group FT TU (20 mg/kg) injection and oral Finasteride perfusion. Data on serum T and DHT, sperm count, sperm mobility and reproductive function were collected and analysed.</p><p><b>RESULTS</b>(1) 5alpha-reductase inhibitor, Finasteride and TU reduced the weight of the testis and epididymis in the experiment groups compared with the negative control (Group C), but TU increased the weight of the prostate while Finasteride decreased it compared with the positive control (Group T). TU combined with Finasteride could counteract the effect of the weight increase of the prostate, but not that of the testis. (2) Finasteride, or Finasteride combined with TU, reduced the DHT but increased the testosterone level in comparison with the control group. (3) Both Finasteride and TU could inhibit epididymal sperm count and reproductive function compared with the control, but the effect was less significant in Group FT than in Group F.</p><p><b>CONCLUSION</b>High dosages of 5alpha-reductase inhibitor, Finasteride, can suppress male reproductive function, but the inhibiting effect could be counteracted by administration of 5alpha-reductase inhibitor along with TU.</p>