[Ultrastructure and morphogenesis of ceroid pigment. I. Phagocytosis and formation of lipid-containing lysosomes in Kupffer Cells after intravenous injection of unsaturated lipids (author's transl)].
Wistar rats were injected intravenously with cod liver oil emulsion. The phagocytosis of these lipids by the Kupffer cells as well as the formation of lipid-containing lysosomes were studied electron microscopically within a period of 5 min to 12 hrs. The emulsified lipids are incorporated into the cytoplasm by membrane-vesiculation. The lipid-containing phagocytic vacuoles (lipophagosomes) were transformed into secondary lysosomes (lipophagolysosomes). This change occurs in two phases. Immediately after phagocytosis the lipophagosomes are provided with lysosomal enzymes by fusion with pre-existent lysosomes (dense bodies) of the Kupffer cells. These are mainly the so-called small homogenous dense bodies which are probably primary lysosomes of the type of "storage granules". In the second phase which begins 15-30 min after the injection; the fusion of lipophagosomes with newly produced primary lysosomes within the Golgi apparatus is predominant. Therefore, the enzyme supply of the phagocytic vacuoles does not occur at once but in small amounts during a longer period. The lipids slowly change into an amorphous electron-dense mass 12 hrs after the injection. Obviously, these changes are the first step to the formation of ceroid pigment.