| Abstract: | Alveolar macrophages obtained by bronchoalveolar lavage of lungs of male and female guinea pigs were incubated with tritium-labelled androstenedione to evaluate the steroid metabolizing enzymes in these cells. The radiolabeled metabolites were isolated and thereafter characterized as testosterone, 5 alpha-androstanedione, 5 alpha-dihydrotestosterone, androsterone, isoandrosterone, 5 alpha-androstane-3 alpha, 17 beta-diol and 5 alpha-androstane-3 beta, 17 beta-diol. Thus, the following androstenedione metabolizing enzymes are present in guinea-pig alveolar macrophages: 17 beta-hydroxysteroid dehydrogenase, 5 alpha-reductase, 3 beta-hydroxysteroid dehydrogenase and 3 alpha-hydroxysteroid dehydrogenase. The predominant androstenedione metabolizing enzyme activity present in alveolar macrophages was 17 beta-hydroxysteroid dehydrogenase. The rate of testosterone formation increased with incubation time up to 4 h, and with macrophage number up to 1.6 X 10(7) cells per ml. Androstenedione metabolism was similar in alveolar macrophages obtained both from male and female guinea pigs. These results suggest that alveolar macrophages may be a site of peripheral transformation of blood-borne androstenedione to biologically potent androgens in vivo and, therefore, these cells may contribute to the plasma levels of testosterone in the guinea pig. |
