ROLE OF LAMININ ON PROLACTIN AND GONADOTROPIN-RELEASE FROM ANTERIOR PITUITARIES OF MALE-RATS

The effect of rat laminin on the release of prolactin (PRL), luteinizi ng hormone (LH) and follicle-stimulating hormone (FSH) from anterior p ituitaries of adult male rats was studied in vitro. Laminin had a bidi rectional 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 obse rved. Laminin did not modify the stimulatory action of thyrotropin-rel easing hormone (TRH) nor luteinizing hormone releasing hormone (LHRH), but the response of FSH to LHRH was inhibited with a maximal effect a t 10(-10)M. To assess its physiological role, the effect of a rabbit a ntibody 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 I gG from normal rabbit serum and medium alone used as controls. No chan ges on the release of LH and FSH were detected. These results suggest that laminin plays a physiologically significant inhibitory role on PR L release at the pituitary level in vitro.