The modification of rat liver regeneration by carcinogens and its reflection by extrahepatic tissues

Liver regeneration is distinctly influenced by the treatment of male Sprague-Dawley rats with 2-acetylaminofluorene or N-methyl-N-nitrosourea on three successive days immediately prior to partial hepatectomy. The latter compound modulates the restorative liver growth, whereas it is strongly inhibited by the hepato-carcinogen 2-acetylaminofluorene. According to their influence on the regenerating liver, both carcinogens delay the post-operative decrease as well as the recovery of the physiological cell renewal in the jejunal and esophageal epithelium. Beside this, the circadian mitotic fluctuation of the esophagus is also altered by the carcinogens after partial hepatectomy like that of the regenerating liver. In contrast to the behaviour of the jejunum and the esophagus, the adrenocortical cell division is temporally elevated by the growth stimulus after partial hepatectomy. This effect is also found after carcinogen pretreatment only. For that reason one can assume that carcinogens produce a growth stimulating response like partial hepatectomy, which is displayed by an increased cell replication in the adrenal cortex. Possibly this phenomenon reflects common systemic mechanisms which indicate the promotory action of partial hepatectomy and chemical promotors as well as that of carcinogens.