Androgen metabolism by rat epididymis. 2. Metabolic conversion of 3H-testosterone in vitro

The epididymis of adult rats metabolizes ³H-testosterone by experiments $\text{in}$$\text{vitro}$. After incubation of slices from epididymal tissue for 2 hrs at 37°C, 8% of the total radioactivity was found in the water-soluble fraction, whereas 92% in the ether soluble fraction (free steroids). The free steroids were examined further and the following metabolites identified: $\text{testosterone}$ (17β-hydroxy-4-androsten-3-one) 10,4%, $\text{androstendione}$ (4-androstene-3,17-dione) 6,2%, $\text{5α-A-dione}$ (5α-androstane-3,17-dione) 7,3%, $\text{DHT}$ (17β-hydroxy-5α-androstane-3-one) 39,3%, $\text{3α-diol}$ (5α-androstane-3α,17β-diol) 22,7%, $\text{3β-diol}$ (5α-androstane-3β,17β-diol) 4,6% and androsterone(3α-hydroxy-5α-androstan-17-one) 8,9%. The relative amount of each metabolite is given in per cent of the total radioactivity in the ether soluble fraction. When segments (caput, corpus, cauda) of epididymis were incubated in the same way, differences in steroid metabolism were demonstrated. Characteristic for caput epididymidis was high formation of DHT (58,4%) and 3α-diol (23,5%). Corpus epididymidis showed lower formation of DHT (50,6%) and 3α-diol (12,7%), but an approximately 3 times higher formation of 5α-A-dione (12,0%) than caput (3,4%) and cauda (3,5%). Cauda epididymis showed the lowest formation of DHT (38,3%), whereas 3α-diol (29,1%) and androsterone (11,4%) formation were relatively high. The ratio between 17β-hydroxy metabolites (DHT and androstanediols) and 17-keto metabolites were much higher in the caput (8,8) than in the corpus (3,2) and cauda (3,6), indicating a higher 5α-reductase activity in this segment.