In the early stage of the experimental liver cancer by azo-dye feeding rats, an appearance of serum alpha-fetoprotein (AFP) was recognized by Hirai and his co-workers ("the first response")., And also so called "oval cells" (Onoe et al) were detectable only in this stage.
We atempted to detect the AFP-producing cells during this stage, by means of immunofluorescent technique.
Fifty adult male rats were fed with 0.06% (w/w)3'-methyl-4-dimethyl aminoazobenzene for 20 weeks. Two of these rats were killed every one week, and their livers were fixed with either 95% cold ethanol or 1% glacial acetic acid in 95% cold ethanol, then, embedded into paraffin after adequate dehydration.
Anti rat AFP horse serum was kindly submitted by Dr. Hirai, Hokkaido Universsty School of Medicine. AFP-producing cells were detected by the direct immunofluorescent method with FITC labelled anti rat AFP conjugate (F/P=1.5).
Immunohistologically, fine granular fluorescence was observed in the cytoplasm of the so called oval cells. Moreover, similar fluorescence was revealed in the cytoplasm of several hepatocytes, unexpectedly.
Fluorescence positive cells in both were scattered in making a few cell group throughout the lobules.
Thus, it has been proved that AFP was produced by not only oval cells but also original hepatocytes in the stage of the first response.
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