Steroids in Germfree and Conventional Rats: Distribution and Excretion of Labelled Pregnenolone and Corticosterone in Male and Female Rats

The distribution of intraperitoneally administered [4‐¹⁴C] pregnenolone and [1,2‐³H] corticosterone were studied in male and female conventional rats at different times after injection of the isotopes. The administered steroids were rapidly excreted into the intestinal tract; 2 h after administration 60—70 % of the given dose was localized in the small bowel, mainly in mono sulphurylated form. The elimination in urine and faeces of intraperitoneally administered [4‐¹⁴C]pregnenolone and [4‐¹⁴C]corticosterone was studied in germfree and conventional, male and female rats. The steroids were excreted as free and conjugated metabolites. The latter were mainly monosulphurylated, and to a smaller extent disulphurylated. No steroid glucuronides were found. As a probable result of the intestinal microbial sulphohydrolase activities conventional rats excreted more free steroids than germfree both in faeces and urine. Male rats excreted more unconjugated and more polar steroids than female. Corticosterone metabolites were monosulphurylated to a larger extent than pregnenolone metabolites; faecal excretion of corticosterone metabolites was quantitatively more important than of pregnenolone metabolites.