Comparative Effects on Rat Liver Cells After Dimethylnitrosamine, 2-Fluorenamine, or Prednisolone Treatment Studied by Electron Microscopy2

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Abstract
Liver cells from rats treated with dimethylnitrosamine, 2-fluorenamine, or prednisolone (pregne-1,4-diene-3, 20-dione, 11ß,17,21-trihydroxy) were examined under the electron microscope. The doses as well as the interval between drug administration and the excision of samples (20 hours) were chosen to represent a metabolic condition, biochemically characterized by a maximal stimulation of the activity of the amino acid incorporation into proteins simultaneously with an increase of the glycogen level of liver. Rats fed ad libitum and those starved for 20 hours were used as controls. The principal observations were: 1) A disorganization of the cisternal endoplasmic reticulum and a decrease in the number of membrane-bound particles after dimethylnitrosamine or 2-fluorenamine treatment. These changes are interpreted as a persistent lesion from an earlier depression period preceding the stimulation. 2) An increase in the amount of free ribosomes after 2-fluorenamine and prednisolone treatment. The importance of this finding in connection with the increased amino acid incorporation is discussed. 3) An enlargement of the spongy endoplasmic reticulum in all three experiments. The hypertrophy of this system could be connected with gluconeogenesis. 4) An increase in the morphological glycogen roughly parallel to the biochemical data. 5) A transitional form between agranular spongy endoplasmic reticulum and granular cisternal endoplasmic reticulum, described in the prednisolone-treated animals. These observations are consistent with the hypothesis that the changes in 2) through 4) after 2-fluorenamine and dimethylnitrosamine treatment are due to a potentiation of the liver cells to the action of glucocorticoids.