Insulin, insulin-like growth factor I (IGF-I) and IGF-II enhance basal and gonadotrophin-releasing hormone-stimulated luteinizing hormone release from rat anterior pituitary cells in vitro.

The role of insulin-like growth factor I (IGF-I) and IGF-II on luteinizing hormone (LH) release is still unclear. The present study was performed to investigate modifications of basal and gonadotrophin-releasing hormone (GnRH)-stimulated (10(-9) mol/l) LH release, induced by 4-h and a 24-h incubation with physiological doses of IGF-I (1, 5 and 10 nmol/l) and IGF-II (5, 10 and 15 nmol/l) in comparison with insulin (0.0017, 0.1722 and 1.722 nmol/l), from primary cultures of male rat anterior pituitary cells. Both during the 4-h and the 24-h incubation, basal and GnRH-stimulated LH release were increased by IGF-I, IGF-II and insulin in a dose-dependent fashion. Present data confirm insulin's capability of potentiating anterior pituitary LH release from dispersed rat anterior pituitary cells in vitro, and reveal similar effects for physiological doses of IGF-I and IGF-II.