Histological characterization and glucose incorporation into glycogen of the pacific oyster Crassostrea gigas storage cells

In order to investigate glycogen metabolism in the oyster Crassostrea gigas the distribution of storage cells in the whole animal was studied before h istological and biochemical characterization. These cells were found mainly in the labial palps, the mantle, and gonadal area and also in gills and th e digestive area. Storage cells from palps, mantle, and gonad presented the same morphological features and the same seasonal glycogen variations. Sto rage cells were isolated from the labial palps and the mantle plus gonadal area of the oyster by enzymatic dispersion and centrifugation through disco ntinuous Percoll gradient. These cells have a modal density of 1.043 g/ml. An ultrastructural study confirmed that glycogen is present in the cytoplas m either as fine particles or sequestered within vesicles. Glucose incorpor ation into glycogen was evaluated in vitro using [U-C-14]glucose: the incor poration in isolated cells increased linearly for at least 8 hours, was pro portional to the cell concentration, and showed saturation kinetics with re spect to the exogenous glucose concentration.