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Effect of EDTA on Leakage of Proteins from Slices of Normal Rat Liver and DAB-induced Hepatoma^*

( Departments of Pharmacology and Biochemistry, University of Toronto, Toronto, Canada)

The leakage of protein from slices of normal rat liver incubated in vitro was found to be significantly increased by the addition of 0.5 per cent ethylenediamine tetraacetate (EDTA) to the medium. The concentrated medium without EDTA revealed essentially the same electrophoretic pattern of soluble proteins as that demonstrable in whole liver, but the addition of EDTA to the medium specifically increased the leakage of an unidentified material, "basic protein 4" apparently derived from the microsomal fraction. Slices of p-dimethylaminoazobenzene-induced hepatoma showed much more variable leakage of protein, which was not consistently or significantly increased by EDTA. Almost all the soluble basic proteins, including "basic protein 4", were markedly diminished or absent from the hepatomas, and the presence of EDTA in the medium did not alter the electrophoretic pattern of the proteins which leaked. The tumors showed much less esterase activity than normal liver, and occasional differences in the electrophoretic pattern of esterases. The findings confirm the clear difference between the DAB-induced hepatoma cells and normal liver cells with respect to the complement of intracellular proteins and show a possible difference with respect to the influence of divalent cations on the permeability of the cell membranes.

^* Supported by grants from the National Cancer Institute of Canada (H.K.) and the Medical Research Council of Canada (R.K.M.).

Received 7/30/63.