Cortisol selectively stimulates pituitary gonadotropin beta-subunit in a primitive teleost, Anguilla anguilla

It has been suggested that in mammals, glucocorticoids, beside their stress -related inhibitory effects on reproductive function, may also play a stimu latory role at the onset of puberty. Using the juvenile female eel as a mod el, we investigated the potential stimulatory role of cortisol (F) on pitui tary gonadotropin (GtH-II). GtH-II levels were measured by RIA, and messeng er RNA (mRNA) levels for alpha- and GtH-II beta-subunits were determined by dot blot using homologous probes. F treatment increased eel pituitary GtH- II content in vivo and in vitro. Using a long term, serum-free primary cult ure of pituitary cells, we studied the direct effect of F on GtH-II product ion. F increased the GtH-II cellular content in vitro in a dose- and time-d ependent manner. The relative potencies of various corticosteroids on GtH-I I were: triamcinolone acetonide > dexamethasone > F >> cortisone and aldost erone, indicating a glucocorticoid specific receptor (GR). F stimulated GtH -II production through a selective increase in mRNA levels for GtH-II beta- subunit; no significant effect was observed on a-subunit mRNA levels. This stimulatory effect of F on GtH-II beta, played out directly at the pituitar y cell level, recalls that of F on FSH beta in the rat. The present study, performed in a primitive teleost at the juvenile stage, suggests that the r ole of F in the positive regulation of gonadotropins at puberty may have ar isen early in vertebrate evolution.