NITRIC-OXIDE (NO) SYNTHASE IMMUNOREACTIVITY IN THE STARFISH MARTHASTERIAS-GLACIALIS

The neuroendocrine system of the starfish Marthasterias glacialis was investigated immunocytochemically using antisera specific for rat neur onal, bovine aortic endothelial, and mouse macrophage, nitric oxide (N O) synthases. Immunoreactivity was detected only with the antibodies s pecific for the neural enzyme, in the ectoneural and hyponeural tissue s of the radial nerve cords and in the basiepithelial plexus and endoc rine cells of the digestive tract. The pyloric stomach showed more imm unoreactive structures than the other digestive organs, with the recta l caeca showing the least activity. Immunoreactive endocrine cells wer e located in the cardiac and pyloric stomachs and in the pyloric caeca . Co-localization of the enzyme immunoreactivity, and the staining for NADPH-diaphorase, demonstrate the presence of NO synthase in echinode rms. These results provide further evidence that NO is a neuronal mess enger of early phylogenetic origin which has been conserved throughout evolution.