Changes in expression of cell cycle regulators and their hepatic lobular distribution in partial hepatectomy-induced regenerating rat liver

Partial hepatectomy (PH) endorses quiescent hepatocytes to reenter the cell cycle. The regenerating liver returns to its preresection weight after 7 d ays, following one or two cell division and maintains nearly its original v olume after then. We focused on the inhibition of further hepatocyte prolif eration, hypothesizing possible involvement of cell cycle upregulators and inhibitors, We studied protein levels in expression of cyclins, cyclin depe ndent kinases (CDKs) and CDK inhibitors (CKIs), and their in situ hepatic l obular distributions in partial hepatectomized rat liver. Cyclin E was expr essed in the same levels in normal liver and after PH, Expression of cyclin A, not detected in normal liver, increased in following times after PH and reached a maximum at 7 day. CDK2 and 4 showed increased expression toward terminal period. Contradictory findings of cyclin A and these CDKs might pl ay an important role in the inhibition of further cell division, although s till unclear. Constitutively expressed CDK6 decreased after 1 day, p18 show ed peak expression within 1 day, and p16, p21, p27 and p57 were stronger at terminal periods. During the expected period of their activity, intranucle ar translocations were observed in cyclin E, p18 and p16. There was no evid ence of regional distribution in hepatic lobular architecture, instead, dif fuse in situ expression, corroborating synchronous event, was found.