Steroids in Germfree and Conventional Rats

The predominant steroids in faeces from germfree rats were identified by gas chromato‐graphy‐mass spectrometry as 3α,11β,15α,21‐tetrahydroxy‐5α‐pregnan‐20‐one and 3α,15α,21‐trihydroxy‐5α‐pregnane‐11,20‐dione. Smaller amounts of 11β,21‐dihydroxy‐5α‐pregnane‐3,20‐dione, 3α,11β,21‐trihydroxy‐5α‐pregnan‐20‐one, 3α,21‐dihydroxy‐5α‐pregnane‐11,20‐dione (tentatively) and another 15α‐hydroxylated steroid, 3α,15α‐dihydroxy‐5α‐pregnan‐20‐one were also identified. None of the 21‐hydroxylated steroids could be found in faeces from conventional rats. Results are given which indicate that the major 21‐hydroxylated steroids are present as 21‐mono‐sulphates and, to a much smaller extent, as disulphates. It is concluded that 15α‐hydroxylation is a major reaction in the metabolism of steroids in the rat and that the intestinal flora plays an important role in the metabolism of 21‐hydroxylated steroids.