Androgens stimulate gonadotropin-II β-subunit in eel pituitary cells in vitro

Abstract Primary cultures of juvenile eel (Anguilla anguilla) pituitary cells were used to study the direct effects of sex steroids on gonadotropin (GtH-II) cell content and release (radioimmunoassay) as well as on mRNAs levels for α and GtH-II β -subunits (dot-blot). Testosterone stimulated GtH-II production in a dose- and time-dependent manner by selectively increasing mRNAs for GtH-II β -subunit but not α -subunit. This positive effect was also induced by non-aromatizable androgens (androstanediol and dihydrotestosterone) but not by estradiol, indicating an androgen-specific effect in the eel. The androgen-specific stimulation of eel GtH-II β appears closer to the regulation of mammalian follice stimulating hormone- β (FSH β ) than that of salmonid GtH-II β or mammalian luteinizing hormone- β (LH β )-subunits. Comparison with previous in vivo experiments suggests multiple sites of action of sex steroids on the brain-pituitary gonadotropic axis for the positive feedback on GtH-II synthesis in this juvenile fish.