Experimental study on the fine structure of chicken liver parenchyme with special references to extrasinusoidal macrophages and sinusoidal blood cells. Part 2. Sinusoidal blood cells in normal and India ink perfused livers.

Leucocytes and thrombocytes in the chicken liver sinusoids were observed under normal conditions and after intravenous India ink perfusion. The monocytes exhibited conspicuous phagocytic activity. At 30 min or earlier and 4 hr after the perfusion, they ingested considerable amounts of the carbon particles, which were deposited in small vacuoles and/or lysosomes. In this study we revealed two transitional forms of the monocyte changing into the Kupffer cell. In one transitional form, which already at 15 min after the perfusion stored considerable amounts of the particles, the ectoplasmic layer was partly differentiated and projected many pseudopodia into the sinusoid. At 48 hr after the perfusion, the other transitional form was attached by its wide basal surface to the endothelial linig and projected well-developed pseudopodia into the sinusoid like the Kupffer cell without, however, storing the carbon particles. These findings are thought to suggest the transformation of the monocytes into the Kupffer cells. Thus we came to the assumption that the Kupffer cells might be replenished: by self-proliferation; by the macrophages from the hepatic parenchyme into the sinusoid; or by transformation from the monocytes circulating into the sinusoid (the "triple origin" as opposed to the "dual origin" of the Kupffer cell). In the earliest stage after India ink perfusion, the thrombocytes exhibited the most striking reaction comparable to the Kupffer cells toward which they were assembled. The India ink particles were taken up into the "surface connected canalicular system" (SCS), which thickened and made vacuolar expansions as the amount of the particles was increased. At 4 hr after perfusion, the particles disappeared from the majority of the thrombocytes, leaving an empty SCS. The India ink particle uptake and storage by the thrombocyte were thought to be temporary phenomena, different from the true phagocytosis of the macrophages.