PHYLOGENETIC ASPECTS OF THE OCCURRENCE AND DISTRIBUTION OF SECRETOGRANIN-II IMMUNOREACTIVITY IN LOWER VERTEBRATE GUT

A novel monoclonal antibody raised against bovine secretogranin II (Sg II) was used in immunohistochemical studies on amphibian (Rana escule nta), reptilian (Podarcis sicula) and avian (Gallus gallus) gut. Sg II immunoreactivity was detected in epithelial and nervous elements. Cel ls immunoreactive for Sg II were examined by double immunostainings to determine whether they might also co-store certain previously known b ioactive amine/peptide substances. Almost all the endocrine cells immu noreactive for bombesin, substance P, neurotensin, gastrin/cholecystok inin, neuropeptide tyrosine (NPY) and calcitonin gene-related peptide as well as some of those immunostained for serotonin, histamine, and p olypeptide tyrosine tyrosine (PYY) also contained Sg II. Sg II-immunor eactive cells varied in number and distribution according to regions o f the gut and animal species. The number of Sg II immunoreactive granu les notably varied not only according to cell type, but also within th e same cell population. Many histamine-, calcitonin gene-related pepti de (CGRP)-, substance P-, PYY-, and neurotensin-immunoreactive neurons also contained Sg II. These were mostly situated in the myenteric ple xus; their distribution pattern varied among the three species. These findings show that, despite being well conserved during phylogeny, Sg II has a heterogeneous distribution.