Luteinizing hormone-releasing factor (LRF)-like immunoreactivity in rat pancreatic islet cells.

Luteinizing hormone-releasing factor (LRF)-like immunoreactive material was demonstrated by the three-layer immunoperoxidase method in formalin-fixed tissue sections of the rat pancreas. Anti-LRF antiserum was prepared in rabbits by immunizing with synthetic LRF coupled to bovine serum albumin (BSA). The immunoreactive site of LRF reacting with antiserum resided between residues Tyr⁵ and Gly¹⁰-NH₂. A positive staining reaction was observed in the islet cells with the use of anti-LRF antiserum after solid phase immunoadsorption with BSA, whereas no staining was observed when adjacent control sections were prepared with anti-LRF antiserum after immunoadsorption with an LRF-BSA conjugate, or with rabbit anti-oxytocin antiserum. LRF-like immunoreactive material was isolated from the rat pancreata by methanol extraction. This material coeluted with synthetic and hypothalamic LRF in cation exchange chromatography on carboxymethyl cellulose, and dilutions of it gave an inhibition curve parallel to that of synthetic LRF in radioimmunoassay. The concentration of LRF-like material in the rat pancreas is 1.1 pg/mg wet weight. These results suggest that LRF or a closely LRF-related peptide is shared by the central nervous system and the gastrointestinal tract.