Tissue distribution of 14C-astaxanthin in the Atlantic salmon (Salmo salar)

Atlantic salmon (Salmo salar) were fed a diet containing 14C-labelled astaxanthin for five subsequent days. Ten days after the last feeding, two fish were sampled and submitted to whole-body autoradiography. A high degree of radioactivity was present in the dorsal cutis, the bile, the intestinal mucosa, the caudal kidney and the developing eggs. An intermediate degree of radiolabelling was found in the muscle and the cranial kidney, while only traces of radioactivity were recorded in the blood, the spleen and the gills. Contrary to the prevailing concensus, the level of astaxanthin and/or metabolites was higher in the myocommata than in the myotome. Furthermore, the substantial radiolabelling in the dorsal cutis strongly suggests that astaxanthin and/or its metabolites show affinity for melanin. Finally, the results give evidence for urinary and biliary excretion of astaxanthin-derived metabolites and for the likelihood of enterohepatic circulation