Alpha-fetoprotein synthesis in relation to structural peculiarities in postnatal and regenerating mouse liver

The localization of alpha-fetoprotein (AFP) and of antigens of liver-cell plasma membrane (Ag I, Ag II and Ag III) was studied in adult, postnatal and regenerating (CCl4 or paracetamol-treated mouse liver). Ag I, Ag II and Ag III were solubilized by Triton X-100 from ghosts of the mouse liver cells. The purification of antigens was performed by gel filtration on Sephadex G-200 or Ultrogel ACA-54 with subsequent treatment of antigenic fractions eluted from the column with 5% HClO4. Ag I and Ag II are common for liver and some other mouse organs, but Ag III is strictly specific for liver. The Ag I is predominantly found in the region of the bile capillaries. Ag II and Ag III are mainly present on membrane adjoining blood sinusoids. The distribution of these three antigens in newborn mouse liver is quite different from that in adult liver and reflects the specific arrangement of hepatocytes at different stages of development - the acinar structure in newborn liver and the plate structure in the adult organ. During regeneration as well as during postnatal development, AFP has been found in areas of marked tissue rearrangement. In both cases, these areas lose the plasma membrane antigens, especially Ag I - the antigen of bile capillary. The reappearance of Ag I on the surface of liver cells coincides with cessation of AFP synthesis and establishment of definitive plate structure. The possible role of liver plate structure in the regulation of AFP synthesis is discussed.