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 blood 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 micrograms/ml), but not with Leu-enkephalin and Met-enkephalin (100 micrograms/ml).