Studies on the Metabolism of C₁₉‐Steroids in Rat Liver: 3. Isolation and Biosynthesis of 5α‐Androstanetriols in Rat Liver Microsomes

The formation of androstanetriols after incubation of testosterone with 105,000 ×g microsomes of adult male rat liver was investigated. The steroids were isolated by thin‐layer chromatography and were identified by gas chromatography‐mass spectrometry as 5α‐androstane‐2β,3α,17β‐triol, 5α‐androstane‐3α,7α,17β‐triol and 5α‐androstane‐3α(and 3β),16α,17β‐triol. Incubation of 2β‐ and 7α‐hydroxytestosterone only gave androstanetriols with a 3α‐configuration while incubation with 6β‐ and 16α‐hydroxytestosterone resulted in the formation of both the 3α‐ and 3β‐epimers of the respective androstanetriols. After incubation with 5α‐dihydrotestosterone the following androstanetriols were isolated: 5α‐androstane‐2β,3α(and 3β),17β‐triol, 5α‐androstane‐3α(and 3β),7α,17β‐triol and 5α‐androstane‐3α(and 3β),16α,17β‐triol. No steroid with a 6β‐hydroxy group could be isolated after this incubation. When 5α‐androstane‐3α,17β‐diol was incubated only 5α‐androstane‐2β,3α,17β‐triol was formed, and 5α‐androstane‐3β,17β‐diol was not hydroxylated in the microsomes. These findings indicate a substrate specificity for the 2β‐, 6β‐, 7α‐ and 16α‐hydroxylases. After incubation of testosterone with 105,000 ×g liver microsomes from male germfree rats the same metabolites were isolated as after incubation with microsomes from conventional rats.