Hemopoietic support capacity of the adult mouse liver: II. Studies in acetylphenylhydrazine-treated mice.

We investigated the hemopoietic support capacity of the liver in intact and splenectomized adult mice treated with three daily injections of acetylphenyl-hydrazine (APH). Packed red cell volumes, liver and spleen weights, numbers of pluripotent hemopoietic stem cells (CFU-S) in blood and liver, and liver histology were evaluated 4,8,12,16, and 20 days after the first injection. We found that 1) splenectomized, APH-treated mice had a greater and more sustained increase in the weights of their livers than the increase found in livers of intact APH-treated mice; 2) APH treatment elicited a much greater increase in the blood and liver CFU-S of splenectomized mice (47 and 42 times normal, respectively) than it elicited in the blood and liver CFU-S of intact mice (4--5 and 4 times normal, respectively); and 3) APH treatment induced numerous foci of hemopoietic tissue in the livers of splenectomized mice. The results of the CFU-S studies can be explained by, and to some extent support, the thesis that the adult mouse liver does not support proliferation of normal CFU-S, but can trap large numbers of circulating CFU-S. In addition, these studies suggest that the livers of adult mice are able to support only limited proliferation of differentiated hemopoietic elements.