title: Further studies on enzymic inactivation of luteinizing hormone- releasing hormone (LH-RH) by peptidases in the rat hypothalamus.
abstract: Luteinizing hormone-releasing hormone (LH-RH) is known to be inactivated by peptidases in the rat hypothalamus with consequent loss of LH-releasing ability. To make a further study of the peptidases' action on the decapeptide, synthetic LH-RH and its [1-9NH2] analogue were incubated with the supernatant hypothalamic fraction containing the enzyme activity. Using an assay system measuring gonadotrophin release in ovariectomized/steroid-primed rats, both LH-RH and the [1-9NH2] analogue were found to be inactivated to different extents after incubation with the fraction, the analogue completely losing both LH- and FSH-releasing activity, and the releasing hormone almost completely losing its LH- and totally losing its FSH-releasing activity. The findings extend the initial studies by showing that the peptidases can remove both the decapeptide's intrinsic LH- and FSH-releasing activity and that these enzymes act on LH-RH at a site other than the C-terminal glycinamide, since they are able to inactivate the [1-9NH2] analogue lacking this residue.
mesh_terms: D000818:Animals; D002369:Castration; D003864:Depression, Chemical; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood*; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D007031:Hypothalamus / Q000201:enzymology*; D007986:Luteinizing Hormone / Q000097:blood*; D010447:Peptide Hydrolases / Q000378:metabolism*; D011374:Progesterone / Q000494:pharmacology; D051381:Rats; D013268:Stimulation, Chemical
chemical_list: D007987:Gonadotropin-Releasing Hormone; D011374:Progesterone; D004958:Estradiol; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D010447:Peptide Hydrolases