<b>PREPROENKEPHALIN A OCCURS IN THE ENTEROCHROMAFFIN (EC) CELLS OF THE PORCINE INTESTINE: AN IMMUNOCYTOCHEMICAL STUDY USING ANTISERA TO MET-ENKEPHALIN-ARG<sup>6</sup>-GLY<sup>7</sup>-LEU<sup>8</sup> AND TO </b><b>SEROTONIN </b>

Abstract

The porcine gut was immunocytochemically examined by using an antiserum against Met-enkephalin-Arg'-Gly'-Len" (Met-enkephalin-8), which is included in the molecule of preproenkephalin A. Met-enkephalin-8-like immunoreactivity was recognized in dispersed endocrine cells as well as in intramural nerve fibers. The immunoreactive cells were most numerous in the duodenum, fewer in the pyloric antrum and still fewer in the lower small intestine. They all coincided with enterochromaffin (EC) cells, which were identified by an anti-serotonin serum applied to adjacent thin sections. In the duodenum, approximately 60 % of the EC cells were also reactive to the anti-Met-enkephalin-8 serum. EC cells were also present in the gastric body and large intestine but they were not reactive to the anti-Met-enkephalin-8 serum. These findings indicate that not all EC cells, but only a subtype which is concentrated in the upper small intestine in the pig, contain preproenkephalin A.