GAMMA-GLUTAMYL CONJUGATION OF 5-HYDROXYTRYPTAMINE (SEROTONIN) IN THE EARTHWORM (LUMBRICUS-TERRESTRIS)

The conversion of 5-hydroxytryptamine to several potential metabolites was examined in the annelid earthworm (Lumbricus terrestris). 5-hydro xytryptamine and some related amines were found to be present in sever al tissues of the earthworm. Injection of 5-hydroxytryptamine into the body cavity of the earthworm resulted in the production of a gamma-gl utamyl conjugate of 5-hydroxytryptamine. Incubations of the anterior n erve cord of the earthworm resulted in the accumulation of considerabl e amounts of 5-hydroxytryptamine and gamma-glutamyl 5-hydroxytryptamin e in the incubation medium. The earthworm did not produce any N-acetyl 5-hydroxytryptamine and only very little 5-hydrorryindoleacetic acid. Experiments involving the injection of radiolabeled 5-hydroxytryptami ne or coinjection of radiolabeled glutamic acid with unlabeled 5-hydro xytryptamine into the earthworm resulted in the production of radiolab eled gamma-glutamyl 5-hydroxytryptamine. This work demonstrates that t he enzymatic conversion of 5-HT in the earthworm is markedly different from that of vertebrates and insects.