Modulation of anterior pituitary luteinizing hormone response to gonadotropin-releasing hormone by insulin-like growth factor I in vitro.

To investigate how much insulin-like growth factor I may modulate the LH response to GnRH.In primary cultures of male rat anterior pituitary cells, the LH response to GnRH (10(-9) M) was evaluated after a 24-hour preincubation with medium alone, IGF-I (1, 5, 10, 15 nM), polyclonal antibody anti-IGF-I (Ab-anti-IGF-I), (1:3,000; 1:10,000), or rabbit serum (1:3,000; 1:10,000) as control.Gonadotropin-releasing hormone-induced LH release from primary cultures of male rat anterior pituitary cells.Insulin-like growth factor I induces a dose-dependent stimulus on the LH response to GnRH. Insulin-like growth factor I at doses of 10 and 15 nM exerted a maximal stimulus, increasing the LH response to GnRH by 30\%. The Ab-anti-IGF-I at both dilutions reduced the LH response to GnRH by 30\%. No effect was exerted by rabbit serum.Present data indicate that IGF-I may enhance the normal LH response to GnRH from rat anterior pituitary glands, suggesting important influences of this growth factor in the modulation of anterior pituitary LH release.