AN AUTORADIOGRAPHIC STUDY OF THE ³H‐URIDINE AND ³H‐THYMIDINE INCORPORATION IN THE REGENERATING MOUSE LIVER

Abstract

An autoradiographic study was made of the 3H‐uridine incorporation into RNA and DNA in nucleus and cytoplasm of parenchymal cells in the regenerating liver of the mouse after a pulse time of 2 hr. After a decreased uptake of precursor into the parenchymal nucleus during the first 6 hr compared with the normal value, incorporation increased and was maximal at 36 hr; normal values were restored at 72 hr. The cytoplasmic labelling, after an initial small decrease, reached a maximum at 12 hr; this changed to normal 48 hr after hepatectomy. RNase‐digestion of the liver sections left a small incorporation in both nucleus and cytoplasm: presumably DNA. This incorporation is maximal at 12 hr over the nucleus and at 24 hr over the cytoplasm. After a 2 hr pulse of 3H‐thymidine, there was a marked uptake of the precursor into DNA about 24 hr after hepatectomy. This was maximal at 48 hr and reached normal values at 72 hr. A small amount of incorporation of 3H‐thymidine into DNA was seen immediately after the operation, and this population of weakly labelled nuclei was still rather large 72 hr later.

Early Increase in Cyclin-D1 Expression and Accelerated Entry of Mouse Hepatocytes into S Phase after Administration of the Mitogen 1,4-Bis[2-(3,5-Dichloropyridyloxy)] Benzene

“…29,30 Indeed, although the time of S phase can be modulated by factors such as sex, age and strain, mouse hepatocytes usually enter S phase between 30 and 42 hours after PH, approximately 12 to 18 hours later than rat hepatocytes. [31][32][33] The finding that changes in immediate early genes/transcription factors such as c-fos, c-jun and c-myc occur almost concomitantly in the two species 21,34 -38 suggests that more stringent check points may exist in mouse liver, that prolong G1 phase of the cell cycle. Our current study showing that the direct mitogen TCPOBOP is able to induce entry of mouse hepatocytes into the cell cycle in only 20 to 24 hours provides clear evidence that the duration of the G1 phase of the cell cycle is dependent on the nature of the proliferative stimulus.…”

Involvement of p21 and p27 in the regulation of CDK activity and cell cycle progression in the regenerating liver

“…The interval between PH and peak DNA synthesis in rodents is a ected by several variables, including species, strain, sex, age and diet (Michalopoulos and DeFrances, 1997;Bucher, 1963). For example, studies in female mice of other strains indicate that peak DNA synthesis occurs 48 h after PH, rather than 36 h, as seen in male BALB/c mice (Paulsen, l990;Lorup, 1977). Consistent with these ®ndings, female p21+/+ mice showed little hepatocyte DNA synthesis as assessed by BrdU uptake at 36 h, but 44.3% BrdU-positive cells were noted at 48 h (Figure 5a).…”

Enzyme activities in regenerating liver of rats

“…During the first cycle of cell division, an increase in RNA transcription occurs, followed by changes in ribosomal and non-ribosomal RNA synthesis. In addition, an increased synthesis of the liver nuclei RNA proceeds, which subsequently appears in the cytoplasm as tRNA, rRNA, and mRNA [6].It was the aim of the present study to follow enzyme variations in the regenerating liver of rats after partial hepatectomy to clarify the mechanism of the biochemical events which take place in the regenerative process. The findings were compared with the enzyme values obtained by examination of fetal rat livers.…”