In Vitro Metabolism of Androgens in Dog Hypothalamus, Pituitary, and Limbic System12

Abstract

The in vitro metabolism of radioactively labeled androstenedione and testosterone in three different areas of the canine central nervous system has been studied. Incubation of androstenedione 4-¹⁴C with minced preparations of dog hypothalamus, pituitary, and limbic system resulted in the formation of ¹⁴C-labeled 5α-androstane-3,17-dione, testosterone, and 17β-hydroxy-5α-androstane-3-one. When testosterone-7-³H was used as substrate, the formation of ³H-labeled 17β-hydroxy-5α-androstane-3-one, androstenedione, and 5α-androstane-3,17-dione were noted. These experiments demonstrate the presence of a 17β-dehydrogenase as well as a steroid Δ⁴-5α-3-keto oxidoreductase system, the latter being involved in the formation of reduced metabolites with high biological activity. These results are discussed in the light of the mechanisms of hormonal action at the target organ level.