[Studies on the metabolism of oestrone and oestradiol-17 beta in the liver of minipigs of different ages and sexes (author's transl)].

After incubation of [4-14C]oestrone (E1) with liver slices from minipigs, the ether-soluble fraction contained [4-14C]oestradiol-17 beta (E2). In the protein-bound fractions, only polar metabolites were found, whereas in the water-soluble fraction the 3-monoglucuronide of oestriol (E1) was the preferred conjugate. When E2 was used as a substrate, E1 was present as main metabolite in the ether-soluble fraction. The radioactive metabolites in the protein-bound and water-soluble fractions were similar to those in the experiments with E1. The metabolism of E1 and E2 was dependent on age. Thus, the rate of conversion of oestrogens was greater in liver tissue of infertile male animals than in fertile males. In contrast, the two steroids were metabolised more rapidly in liver of fertile female minipigs than in infertile female animals. In fertile animals, the metabolic pattern of oestrogens in the ether-soluble, the protein-bound and the water-soluble fractions showed sex dependence: In females, E1 and E2 were metabolised to a greater extent by liver slices than in males. On the other hand, in experiments with male minipigs, E3-3-monoglucuronide was the only metabolite in the water-soluble fraction, whereas liver slices of female animals not only form E3-3-monoglucuronide, but also the 3-glucuronides of E1 and E2. The results described here show that, in liver tissue of minipigs, the oxidoreduction of E2 and E1 is the predominant reaction; in contrast to human liver, hydroxylation reactions play only a minor role. It may be concluded that there are differences in the metabolism of steroid hormones in man and minipig.