The regional distribution and the chemical, chromatographic, and immunologic characterization of motilin brain peptides: the evidence for a difference between brain and intestinal motilin-immunoreactive peptides

Open Access
Publisher Website
Google Scholar
Abstract
Motilin-like immunoreactive peptides (MLIPs) have been detected in the brain by radioimmunoassay (RIA), (Yanaihara, C., H. Sato, N. Yanaihara, S. Naruse, W. G. Forssman, V. Helmstaedter, T. Fujita, K. Yamaguchi, and K. Abe (1977) Adv. Exp. Biol. Med. 106: 269-283; Chey, W.Y., R. Escoffery, F. Roth, T.M. Chang, and H. Yajima (1980) Regul. Pept. Suppl. 1:519; O''Donohue, T. L., M.C. Beinfeld, W.Y. Chey, T.M. Chang, G. Nilaver, E.A. Zimmerman, H. Yajima, H. Adachi, M. Roth, R.P. McDevitt, and D.M. Jacobowitz (1981) Peptides 2: 467-477). Previous studies (O''Donohue et al., 1981) demonstrated that MLIPs in rat brain probably differ chemically from porcine intestinal motilin (PIM), the first motilin peptide isolated. The possibility that this rat-pig difference represents a species difference was not examined in the previous study (O''Donohue et al., 1981), neither was the question of the cross-species distribution of MLIP. This study was initiated to examine brain MLIP distribution by RIA in three additional species: cow, pig, and guinea pig. The question of rat-pig species differences was addressed by characterizing MLIP in the brains of these species in comparison to PIM. By RIA, MLIP''s were widely distributed in the brains of all species examined. MLIP concentration was highest in rat brain and lowest in pig brain. Some motilin antisera consistently detected less or no MLIPs in some brain regions of all species. Rat pituitary, pineal gland, and retina has substantially higher MLIP concentrations than did brain. MLIPs were abundant throughout the rat gastrointestinal tract and in some other peripheral organs. Rat, cow, and pig brain extracts separated by gel filtration chromatography contain a peak of MLIP similar in size to PIM. MLIP immunoreactivity in these fractions from rat and cow were largely or completely peptidase sensitive. On high pressure liquid chromatography (HPLC), MLIP similar in size to PIM from rat, cow, and pig brain elutes as discrete peak, well separated from PIM. Other MLIPs, smaller in size than PIM, also separate from PIM on HPLC and are much less protease sensitive. In conclusion, a brain MLIP similar in size to PIM is present in the brains of several vertebrate species. However, based on the immunological and chromatographic evidence presented, the sequence to brain MLIP probably differs from that of PIM (or it has been post-translationally modified). The extent of this difference and its implication for the functional role of MLIP in brain remain to be determined.