Effect of androgens and melatonin on glucocorticoid receptor regulation in toad testes.

REGUEIRA ELEONORA; SCAIA MARIA FLORENCIA; CEBALLOS NORA RAQUEL

Carlos Paz, Córdoba.

Congreso; XLIV Reunion Anual de la Sociedad Argentina de Investigacion Bioquimica y Biologia Molecular.; 2008

SAIB

Bufo arenarum is an anuran amphibian characterized by having the highest concentration of plasma glucocorticoids (GC) during the breeding season. The sensitivity to GC is regulated by the number and affinity of the glucocorticoid receptor (GR). A cytosolic GR has been described in Leydig and Sertoli cells. Seasonal studies of GR apparent number of binding sites have shown significant differences during the year. Melatonin and androgens have been reported to regulate GR expression in other biological systems, so the aim of the present work is to analyse the effect of these hormones in the amount of GR in B. arenarum testicular cells. The number of binding sites and GR protein levels (Western Blot analysis) were measured in testes homogenate after in vitro incubation of testicular fragments in the following conditions: testosterone (0,1 uM), dihydrotestosterone (0,1 uM), casodex or hydroxyflutamide (testosterone receptor antagonists) (10 uM), cyanoketone (a 3beta-hydroxysteroid dehydrogenase inhibitor) (10 uM), melatonin (0,2 and 0,9 nM). Neither androgens nor androgens antagonists modified the number of binding sites. In addition, the inhibition of steroidogenesis does not affect the number of receptors. On the other side, 0,2 nM melatonin decreases the number of binding sites and GR protein level suggesting that this circadian responding hormone might regulate the GR in the toad testes.