Androgen metabolism in oyster Crassostrea gigas:: evidence for 17β-HSD activities and characterization of an aromatase-like activity inhibited by pharmacological compounds and a marine pollutant

The annual reproductive cycle of oyster Crassostreo gigas depends on environmental factors. but its endocrine regulations are still unknown. Sexual steroids play important roles at this level in vertebrates, and some estradiol effects have been described in invertebrates such as bivalve mollusks. To question these roles in invertebrates, we studied androgen metabolism in C. gigas. Incubations of tissue homogenates with C-14-steroids such as androstenedione (A), testosterone (T), estrone (E-1) and estradiol (E-2), followed by TLC and HPLC, provide evidence for 17 beta -hydroxysteroid dehydrogenases (17 beta -HSDs. conversions of A into T, T into A, E-1 into E-2 and E-2 into E-1) and aromatase-like (A into E-1) activities. The latter activity was further characterized by tritiated water release assay; it was time- and temperature-dependent. Furthermore, this oyster aromatase-like activity was inhibited by 4-hydroxyandrostenedione (IC50x 0.456 muM) and by other pharmacological compounds including specific cytochrome P450 inhibitors (MR20494, miconazole) and a marine pollutant (tributyltin). (C) 2001 Elsevier Science Ltd. All rights reserved.