Funtional Similarities between the Cytoplasmic Organelles of Melanocytes and the Mitochondria of Hepatocytes

IN an earlier communication 1 , it was reported that the cytoplasm of melanocytes, located in the liver of the amphibian Amphiuma , is packed with large organelles containing melanin granules in varying numbers. These melanocytes have few mitochondria and no visible ribosomes, in contrast to the hepatocytes which present the familiar organelles in large numbers. The sharp structural differences between the respective liver cells evoked our interest in comparing the functions of the organelles which abound in each. The insight to be gained from such investigations seemed to transcend the particular melanocytes under discussion: normal cells with similar structures are being seen in other organs 2–4 and in other vertebrates 5,6 , while abnormal metabolism of melanins is being encountered in human diseases ranging from neoplasia 7 to extrapyramidal disorders of the brain 8,9 .