Synthesis and turnover of DNA in hepatocytes of neonatal rats

Abstract

The incorporation of 3H-thymidine has been studied in the hepatocytes nuclei of rats during the first 3 days of life. The synthesis of DNA which occurs in lWO of nuclei after a single injection of the labelled precursors 2 h after birth, cannot be considered as premitotic since:(i) The hepatic cell number is constant during the first 3 days of life.(ii) The mitotic index is less than O.l(:,, 20 times lower than that expected on the basis of the labelling index and of the length of cellular cycle.(iii) The percentage of labelled nuclei does not increase in the following 3 days.(iv) the average number of grains per nucleus is unchanged for 18 h after the injection, a period longer than an entire cellular cycle (13 h).This synthesis is better explained as due to an increase of DNA content per nucleus, previously described, in the hepatocytes during the first 3 days of life.After 20 h of life (18 h after label injection) a decrease of label of about 30",, takes place without variation of DNA-Feulgen dye content per nucleus. It is concluded that synthesis and turnover of DNA are present in the hepatocytes nuclei and that these processes are probably related to the functional maturation of the cells.

Polyploidy and liver proliferation: Central role of insulin signaling

“…In parallel with this process, there is a progressive decline in cellular proliferation. For example, the DNA synthesis rate in rats two hours after birth is high, with 18% of the hepatocytes incorporating 3 H-Thymidine 15 and three weeks after birth, ∼9% of hepatocytes show evidence of DNA synthesis; however, within six weeks DNA synthesis is detected in only few hepatocytes (∼0.05%) as is similar to the situation in the normal adult liver. The onset of hepatocyte polyploidy is clearly correlated with this end of the proliferative state.…”

Cell proliferation studies in rat prostate I. the proliferative role of basal and secretory epithelial cells during normal growth

“…In these experiments a relatively long 3HTdR pulse period (4 hours) was deliberately chosen, in order to demonstrate that labelled secretory and basal cells were able to progress to mitosis. The uptake of 3HTdR did not, therefore, appear to be associated with unscheduled DNA synthesis or long-lived thymidine pools, two processes that have been thought to be unrelated to an immediate progression into mitosis [22,23].…”

Hepatocytes Polyploidization and Cell Cycle Control in Liver Physiopathology

“…In rodents, through 14th embryonic development day (e.g., E14), most hepatoblasts are bipotent with the ability to differentiate into hepatocytes or into biliary cells; by E15 most hepatoblasts are committed to the hepatocyte lineage [38, 39]. During the remaining period of gestation and the first four postnatal weeks, hepatoblasts acquire functions of differentiated hepatocytes, and this period is correlated with a severe decline in proliferative state [40, 41]. During previous studies, we have observed that the liver is almost exclusively made up of diploid hepatocytes for the first three weeks after birth.…”