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Immunoreactive Met‐Enkephalin Arg 6 in Rat Brain, and Bovine Brain, Gut, and Adrenal
Author(s) -
Giraud A. S.,
Dockray G. J.,
Williams R. G.
Publication year - 1984
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1984.tb05378.x
Subject(s) - radioimmunoassay , trypsinization , medicine , endocrinology , size exclusion chromatography , met enkephalin , trypsin , striatum , prohormone , enkephalin , neuropeptide , biochemistry , chemistry , biology , enzyme , hormone , receptor , opioid , dopamine
Antibodies directed against the Met‐enkephalin‐related hexapeptide, Met‐enk Arg 6 , have been used in radioimmunoassays in the characterization of material in rat brain, and bovine striatum, colon, and adrenal medulla. Met‐enk Lys 6 reacted 0.27 relative to Met‐enk Arg 6 , but Leu‐enk Arg 6 and C‐terminal extensions or deletions of Met‐enk Arg 6 showed less than 0.02 immunoreactivity. In rat brain, the concentration of Met‐enk Arg 6 ‐like immunoreactivity was <20 pmol · g −1 in all regions, but after trypsinization of tissue extracts there were up to 80‐fold increases in immunoreactivity as a result of cleavage of C‐terminally extended forms. The tryptic product eluted as Met‐enk Arg 6 on gel filtration. In control extracts of rat brain there were at least three immunoreactive forms of Met‐enk Arg 6 ; one eluted in the position of the hexapeptide standard on gel filtration and HPLC while the others had properties of N‐terminally extended forms. In bovine striatum and colon the hexapeptide‐like material predominated; but in bovine adrenal extracts, there were relatively low concentrations of the hexapeptide and, instead, the dominant immunoreactive forms corresponded to two components that were probably N‐terminally extended variants. Trypsin again produced marked increases in immunoreactivity. HPLC studies indicated that Met‐enk Arg 6 Phe 7 ‐and Met‐enk Arg 6 Gly 7 Leu 8 ‐like immunoreactive peptides were important substrates in bovine brain for the production of hexapeptide immunoreactivity after trypsin. The differences in the patterns of immunoreactive forms in bovine adrenal, colon, and brain are consistent with tissue variations in the pathways of posttranslational processing of the precursor molecules.