REGULATION OF GLUCOCORTICOID PRODUCTION IN THE TOAD Rhinella arenarum

E. REGUEIRA AND N. R. CEBALLOS

Ann Arbor

Simposio; ISAREN 2011: 7th International Symposium on Amphibian and Reptilian Endocrinology and Neurobiology; 2011

Amphibians present seasonal changes in plasmatic concentrations of glucocorticoids (GCs), presenting the highest levels during the reproductive period. Rhinella arenarum is characterized by having an androgen-dissociated breeding pattern with the lowest concentration of testosterone during the breeding period and the highest during the pre-reproductive period. Also, GCs regulate the production of testicular androgens by inhibiting the Cytochrome P450c17 (steroid 17 alpha-hydroxylase/17,20 lyase) enzime. The aim of this work was to analyze if androgens, which in this species are only from testicular origin, regulate GC production in the adrenal gland of R. arenarum. Adrenals from adult male toads were incubated in vitro with physiological concentrations of testosterone corresponding to the reproductive (10 nM) and pre-reproductive (100 nM) period. After 24 h, adrenals were incubated for 1 h in fresh medium without hormones and corticosterone production in the media was evaluated by radioimmunoassay. The treatment with 100 nM testosterone produced a decrease in the corticosterone synthesis respect the incubation with 10 nM. In R. arenarum an interaction between the gonadal and adrenal system seem to be present, while GC down-regulate the testosterone production during the reproductive period, androgens might regulate the GC production during the pre-reproductive period.