Role of laminin on prolactin and gonadotrophin release from anterior pituitaries of male rats.

The effect of rat laminin on the release of prolactin (PRL), luteinizing hormone (LH) and follicle-stimulating hormone (FSH) from anterior pituitaries of adult male rats was studied in vitro. Laminin had a bidirectional effect on basal release of PRL, being stimulatory at 10(-12)M and inhibitory at 10(-9) and 10(-8)M. LH release was only stimulated by the 10(-12)M concentration and no changes in FSH release were observed. Laminin did not modify the stimulatory action of thyrotropin-releasing hormone (TRH) nor luteinizing hormone releasing hormone (LHRH), but the response of FSH to LHRH was inhibited with a maximal effect at 10(-10)M. To assess its physiological role, the effect of a rabbit antibody to laminin on the release of PRL, LH and FSH was also studied. IgG anti-laminin at 2 x 10(-7)M had a highly significant stimulatory effect on PRL release after 3 and 5 hr of incubation, as compared to IgG from normal rabbit serum and medium alone used as controls. No changes on the release of LH and FSH were detected. These results suggest that laminin plays a physiologically significant inhibitory role on PRL release at the pituitary level in vitro.