DNA synthesis and nucleolar organizer regions circadian rhythm in mouse regenerating liver hepatocytes

DNA synthesis and Nucleolar Organizer Regions (NORs) were studied in C3HS i nbred mice standardized for periodicity analysis. Immunohistochemical detec tion of Bromodeoxyuridine (BrdU) incorporated into DNA with a monoclonal an tibody and silver staining of NORs (AgNORs) were assessed by means of a dig ital image analysis system in histological sections of regenerating liver. Tissue samples were obtained at different times after hepatectomy along a c ircadian span. The results showed a strong correlation of values between DN A synthesis (BrdU labelling index) and AgNOR numbers, with higher counts du ring the activity period of animals at 00:00/38 and 04:00/42 hours Time of Day / Hours Post-Hepatectomy (TD/MPH), being the differences with other tim e points highly significant. Our observations demonstrate the existence of a strong correlation of DNA synthesis measured by BrdU incorporation and Ag NOR numbers with a defined circadian rhythm in mouse regenerating hepatocyt es.