A physiological role for luteinizing hormone release-inhibiting factor of hypothalamic origin.

A 12 KD peptide, LH release-inhibiting factor (LHRIF), extracted from rat hypothalamus has been shown to inhibit LHRH-stimulated LH release from cultured anterior pituitary cells. In the present study this partially purified material also blocks LHRH-stimulated LH release in pentobarbital-blocked proestrous rats. Administration of a polyclonal antiserum to partially purified LHRIF potentiates estrogen-induced LH release and antagonizes the inhibitory effect of estrogen and progesterone on LH release in ovariectomized rats. These results suggest that a hypothalamic LHRIF plays a physiological role in regulating LH release in the rat.