Extreme nucleoside concentrations in a marine annelid: A novel nucleoside storing cell in the polychaete Nereis virens

A new type of free coelomic cell was isolated from the coelomic fluid of the polychaete Nereis virens. This cell type was present only during sexual maturation and only in males with fully developed spermatozoa. In vivo acridine orange staining and electron microscopy showed that this cell type consists mainly of a large acidic vacuole with a very low proportion of cytoplasm. This cell type stores extremely high concentration of purine nucleosides reaching concentrations of > 700 millimolar on a cell weight basis. The nucleoside concentrations are the highest reported from any living cell so far. Inosine (280-711 μmol/g cell mass), guanosine (8-109 μmol/g), deoxyinosine (3-26 μmol/g) and deoxyguanosine (0.05-0.70 μmol/g) were the main nucleosides. The spectrum of nucleosides reflected that of the surrounding coelomic fluid suggesting their exogenous origin. In culture, labeled guanosine was effectively concentrated by the cells. The vacuole is the most likely storage compartment for the nucleosides and its acidic pH provides higher nucleoside solubility and prevents back diffusion by protonation of the nucleosides.