Presence of luteinizing hormone releasing hormone (LHRH) in milk.

Evidence is presented a luteinizing hormone-releasing hormone (LHRH)-like substance exists in milk of the rat and that this substance is transferred to the offspring during suckling. This milk "LHRH" generates an inhibition curve parallel to authentic LHRH in the LHRH radioimmunoassay (RIA) and coelutes, to a significant extent, with LHRH upon Sephadex G-25 chromatography. An increase in LHRH-like immunoreactivity (LHRH-LI) can be detected in both the stomach and plasma of infantile rats during suckling. Available ovarian LHRH receptors increase in the pups after separation of the mother and return to basal values following suckling. This change is prevented by i. v. administration of an LHRH antiserum. Milk LHRH stimulates gonadotropin release in vitro and inhibits both gonadotropin-induced steroid secretion from granulosa cells in culture and the binding of LHRH to ovarian membranes.