INVESTIGADORES
SOMOZA Gustavo Manuel
congresos y reuniones científicas
Título:
Androgen synthesis in the silverside Odontesthes bonariensis.
Autor/es:
MARTÍN BLASCO; GUSTAVO M SOMOZA; DENISE VIZZIANO
Lugar:
Saint Malo. Francia
Reunión:
Congreso; 8th International Symposium on Reproductive Physiology of Fish; 2007
Resumen:
BACKGROUND: Early testis differentiation in fish with genetic sex determination seems not to be mediated by androgens. However, the role of androgens as early mediators of sex determination and/or differentiation in testes of fish with temperature sex determination (TSD) could not be excluded. We choose the silverside Odontesthes bonariensis as a model with a strong TSD and investigated the androgen production in several organs including testes, ovaries, kidneys and liver of juvenile and adult fish. We observed that 11-oxygenated androgens are produced almost exclusively in testes. Next studies will be directed to determine if 11-oxygenated androgens are able to be produced by male gonads during the determining and differentiating time of the species.   METHODS: Explants of immature, in spermatogenesis and spermiant testis and of immature ovaries of O. bonariensis were incubated in the presence of the following precursors: [1,2,6,7-3H]-17-hydroxy-4-pregnene-3, 20-dione (3H-17P), [1â-3H] androstenedione (3H-A4) and [1,2,6,7-3H] testosterone (3H-T). Brain, liver and kidney were incubated with 3H-A4. The metabolites were analyzed by TLC, revealed by autoradiography, and further analyzed by HPLC and co-crystallization with authentic standards. Gonads were fixed for classic histology in order to determine their stage.   RESULTS: The main metabolites produced by juvenile and adult testis were adrenosterone, 11-ketotestosterone (11KT) and 11â-hydroxy androstenedione (11OHA4). In presence of 17P, immature testis produced 11KT as major androgen whereas testes from sexually mature fish produced mainly 11OHA4. Spermiating testis incubated with 17P produced 11OHA4 as major steroid whereas the same testis incubated with T presented 11KT as the most prominent steroid. None of these 11-oxygenated androgens were detected in immature females neither when incubated with 17P4 nor A4. Liver did not produced any of the 11-oxygenated androgens found in testis but kidney produced minor amount of 11OHA4.   CONCLUSION: As in other teleost fish, testes of differentiated silverside produced 11-oxygenated androgens as major androgens while ovaries did not produced these kind of steroids. 11KT and 11OHA4 seems to be involved in the regulation of spermatogenesis as it was found in other fish, and are prominent during spermiating time opening the question about their role during this period. A part from masculine gonads only the kidney had the possibility to produce 11OHA4, but in little amount. The fact that 11-oxygenated androgens are produced mainly by testes will allow us to study the androgen synthesis capacity during the very early stages of  testes development in all-male silverside induced by temperature.