Immunochemical demonstration of Eisenia tetradecapeptide, a bioactive peptide isolated from the gut of the earthworm Eisenia foetida, in tissues of the earthworm

The quantity and localization of Eisenia tetradecapeptide which was isolated from the gut of the earthworm Eisenia foetida were examined in tissues of the same species by enzyme-linked immunosorbent assay and immunohistochemistry. Analysis by enzyme-linked immunosorbent assay showed that Eisenia-tetradecapeptide-like immunoreactivity was present in both the central nervous system (cerebral ganglion, subesophageal ganglion, ventral ganglia, and ventral nerve cord) and the gut (esophagus, crop, gizzard, and intestine). The central nervous system contained a higher amount of Eisenia-tetradecapeptide-like immunoreactivity (1.3 pmol/mg wet weight) than the gut (0.2-0.6 pmol/mg wet weight). Eisenia-tetradecapeptide-like immunoreactivity was scarcely detected in the body-wall muscle, nephridia, and sexual organs (testis, ovary, seminal vesicle, and ovisac). Immunohistochemical analysis demonstrated that intense Eisenia-tetradecapeptide-like immunopositive cells and nerve fibers were present in the central nervous system. Immunoreactivity was found in the epithelial cells lining the esophagus and in the submucous plexus in various parts of the gut. Thus, the present study suggests that Eisenia tetradecapeptide is a neuropeptide and/or peptide hormone present in both the central nervous system and the gut of the earthworm and that its role involves the regulation of gut motility.