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Studies on the Intracellular Composition of Livers from Rats Fed 2-Acetylaminofluorene^*

A. K. Laird and E. C. Miller

( McArdle Memorial Laboratory, Medical School, University of Wisconsin, Madison 6, Wis.)

1. Livers from rats fed 2-acetylaminofluorene for various times up to and including gross tumor development (4, 7, 14, 25, and 27 weeks) were homogenized and separated into nuclear, large granule, small granule, and supernatant fluid fractions, and each fraction was analyzed for protein nitrogen, nucleic acids, and riboflavin. The results were expressed in terms of the amount per average cell and per average liver. Livers from rats taken at the beginning of the experiment or maintained on the same diet without the carcinogen for 34 weeks and liver tumors induced by 2-acetylamino-fluorene were analyzed in the same manner.

2. In general, the levels of protein, pentosenucleic acid, and riboflavin, when expressed on a cell basis, fell to minimum values at 4 weeks. These minimum values were either maintained or there were slow increases toward the levels found in normal liver cells. In general, the tumor cells contained about half as much of each constituent as was found in the liver cells after 4 weeks of treatment. The damaged liver cells and the tumor cells contained the same amount of desoxypentosenucleic acid as did normal liver cells.

3. At 4 weeks the number of cells per liver was essentially normal, but the cells were only about two-thirds as large as the usual liver cell. Thereafter, the cells retained their small size, except for some very large cells which arose late in the experiment, but the number of cells per liver was nearly twice the initial level at 7 weeks, and nearly 3 times the normal level at 14 weeks.

^* This work was supported in part by a grant-in-aid from the American Cancer Society upon recommendation of the Committee on Growth of the National Research Council, by an institutional grant from the American Cancer Society, and by the Alexander and Margaret Stewart Trust Fund.

Postdoctoral fellow of the United States Public Health Service, 1949–50.

Received 2/24/53.