Nerve elements containing met-enkephalin-Arg⁶-Gly⁷-Leu⁸-like immunoreactivity in canine pancreas - A histochemical study

Canine pancreas was examined by Sternberger's peroxidase-antiperoxidase method using an antiserum against Met-enkephalin-Arg⁶-Gly⁷-Leu⁸ (Met-Enk-Arg-Gly-Leu), an opioid octapeptide included in preproenkephalin A. Immunoreactive Met-Enk-Arg-Gly-Leu-containing nerve terminals with beaded appearance were demonstrated to be juxtaposed to small vessels of the exocrine and endocrine pancreas. Eighty-five out of 174 ganglion cell somas in the pancreas were immunopositive. The specific immunostaining was absorbed by preincubation of the antiserum (dilution, 1:2000) with Met-Enk-Arg-Gly-Leu (50 μg/ml), but not with Leu-enkephalin and Met-enkephalin (100 μg/ml).