Studies on the Metabolism of C₁₉‐Steroids in Rat Liver

Abstract

The formation of androstanetriols after incubation of testosterone with 105,000 x 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 5 a-androstane2p,3a,l7p-triol, 5u-androstane-3a,7a,l7,!?-triol and 5a-androstane-3a(and 3/?),16~,17p-triol. Incubation of 2p-and 7a-hydroxytestosterone only gave androstanetriols with a 3a-configuration while incubation with 6,9-and 16a-hydroxytestosterone resulted in the formation of both the 3a-and 3B-epimers of the respective androstanetriols. After incubation with Ba-dihydrotestosterone the following androstanetriols were isolated : 5a-androstane-2/?,3a(and 3p),17p-triol, 5a-androstane-3a(and 3,!?),7a,17/3-triol and 5a-androstane-3a(and 3,3),16a,17~-triol. No steroid with a 6p-hydroxy group could be isolated after this incubation. When 5a-androstane-3a,17,4-diol was incubated only 5a-androstane-2fl,3a,l7p-triol was formed, and 5cc-androstane-3p,l7p-diol was not hydroxylated in the microsomes. These findings indicate a substrate specificity for the 2p-, 6g-, 7a-and 16a-hydroxylases.After incubation of testosterone with 105,000 x g liver microsomes from male germfree rats the same metabolites were isolated as after incubation with microsomes from conventional rats.Several studies have shown that saturated C,,O, steroids are formed during the metabolism of testosterone in rat liver. These polar metabolites have been detected after incubation of mince [l] and microsome preparations [2--41 as well as after liver perfusion [5] with testosterone.

Mass Spectrometric Fragmentation of Trimethylsilyl and Related Alkylsilyl Derivatives

“…When an additional TMSO group is present at the 3‐position ( 132 ), the situation changes and a group of three ions ( m/z 129, 142 and 143) appear (Fig. b, a contribution to m/z 129 ( n ) is from the D‐ring), said to be typical of steroids with 2‐TMSO groups (Eriksson & Gustafsson, ; Gustafsson et al, ). These ions are also prominent in the spectra from 2α,3α‐dihydroxy‐pregnan‐20‐one (Eriksson et al, ) and 2β,3β,17β‐trihydroxy‐5α‐androstane TMS ether.…”

“…Proposed mechanisms for their formation, consistent with labeling data, are shown in Schemes and respectively. However, the ions do not appear in the spectra of some more highly‐substituted steroids such as those containing 17‐TMSO and 17 C═O groups (Gustafsson & Lisboa, , , , ; Gustafsson et al, ).…”

“…Fragmentation, in this case, appears to be largely directed by charge localization remote from the 7‐TMSO group because, in the corresponding spectrum of 7α‐TMSO‐cholest‐4‐en‐3‐one ( 158 ), a prominent TMS‐containing ion appears at m/z 224 whose formation can be explained by the mechanism outlined in Scheme (Axelson et al, ). The 7‐hydroxy‐containing steroids, 3α‐(and β‐),7α,17β‐trihydroxy‐5α‐androstane (Gustafsson et al, ) and 7α‐hydroxy‐pregn‐4‐en,3,20‐dione (7α‐hydroxy‐progesterone) (Gustafsson & Lisboa, ) failed to yield any diagnostic ions for hydroxylation in the 7‐position.…”

“…Some 16(α and β),17β‐dihydroxyandrostanes (e.g., 168 ) produce a major ion, often the base peak, at m/z 191 ( ed ) (Gustafsson et al, ,,; Lisboa, ; Lisboa et al, ) whose mechanism of formation has been discussed by Gustafsson et al () and is outlined in Scheme .…”

Gender, Age and Microbial Status Influence upon Intestinal Cell Kinetics in a Compartmentalized Manner: An Experimental Study in Germfree and Conventional Rats

“…In an early study by Wostmann et al (17), it was shown that GF rats on a restricted diet had a serum testosterone level that was 2.5 times higher than in Conv rats. It is well established that the presence of intestinal microbial ora gives rise to metabolites of testosterone, which are not found in GF counterparts (25). Whether these metabolites exert altered androgenic stimuli other than testosterone itself has not been satisfactorily investigated.…”