Chromatin structure, number, volume and position of nucleoli in rat hepatocyte after treatment with benzo(a)pyrene and N-acetylaminofluorene

Abstract

In Wistar rat liver, after the acute treatment with two carcinogenic substances - benzo(a)pyrene and N-acetylaminofluorene - changes involving the nucleus are observed 2, 4 and 6 hours later. The electron-microscopic aspect of the chromatin, as well as the number and volume of nucleoli are altered. The parameters considered (number, mean volume and total nucleolar volume related to nuclear number) showed a movement of the nucleoli inside the nucleus from and towards the nuclear membrane, as a reaction to the chemical oncogenic stress. Thus, there is a relative variation of the number of nucleoli which come into contact with the nuclear envelope or occur within the nucleus. The number and volume are increased 2 hours after the treatment in the case of the nucleoli placed close to the nuclear membrane; the same process is observed after 4-6 hours in nucleoli located centrally. In the experiments described, the reversibility of most of these changes 24 hours after the treatment appears as being the rule.