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Histochemical Studies on Rat Liver Proteins during 4-Dimethylaminoazobenzene Carcinogenesis¹

Laboratoires de Recherche, Institut du Cancer de Montréal, Hópital Notre-Dame, and Département d'Anatomie, Université de Montréal, Montréal, Canada^,4

Areas of preneoplastic livers characterized by intense RNA staining apparently represent the sites of neoplastic transformation. These hyperbasophilic foci, as well as the hepatomas, showed a marked decrease in the staining intensity of the cytoplasmic proteins in sections stained by the mercury-bromophenol blue method or the Millon reaction. Following extraction of the RNA, however, protein stainability in these sites was comparable to that of surrounding parenchyma. Radioautographic studies further indicated that hyperbasophilic foci and hepatomas do not differ from the surrounding tissue in the labeling of cytoplasmic proteins by tritiated leucine.

These results were interpreted as indicating the presence in sites of neoplastic transformation and liver tumors of some unusual RNA which binds to and masks the cytoplasmic proteins.

¹ This investigation was supported by grants from the National Cancer Institute of Canada. A preliminary report of this work was presented at the 58th Annual Meeting of the American Association for Cancer Research held in Chicago, Ill., April 13 to 15, 1967 (2).

² Fellow of the National Research Council of Canada. Present address: Département d'Anatomie, Faculté de Médecine, Université de Sherbrooke, Sherbrooke, Québec, Canada.

³ Research Associate of the National Cancer Institute of Canada.

⁴ Mailing address: Institut du Cancer de Montréal, Hópital Notre-Dame, 1560 est, rue Sherbrooke, Montréal, Canada.

Received 4/30/69. Accepted 12/19/69.