Accumulation of immunomodulatory laminaran (beta(1,3)-D-glucan) in the heart, spleen and kidney of Atlantic cod, Gadus morhua L

The tissue distribution of H-3- and FITC-laminaran in Atlantic cod, Gadus morhua L., was investigated after intravenous administration. Liquid scintillation counting and whole-body autoradiography revealed a substantial accumulation of H-3-labelled laminaran in the heart throughout the experimental period (1 h to 12 days). High amounts of the immunomodulator were also present in the spleen, anterior kidney and posterior kidney during the study. Renal excretion and intestinal exsorption were the main elimination pathways. Fluorescence microscopic examination revealed accumulation of FITC-labelled laminaran in macrophages in the kidney and ellipsoid sheath cells (macrophages and reticular cells) in the spleen. Furthermore, endothelial entrapment in the heart was pronounced. Endothelial cells in the kidney also contained the FITC-labelled immunomodulator. Immunohistochemical analysis, using anti-beta(1,3)-D-glucopyranose antibody, also showed endothelial uptake of laminaran in the heart. The present investigation shows that laminaran accumulates and is retained in immunologically relevant cells in the Atlantic cod.