Abstract
Partial hepatectomy (PH) endorses quiescent hepatocytes to reenter the cell
cycle. The regenerating liver returns to its preresection weight after 7 days,
following one or two cell division and maintains nearly its original volume
after then. We focused on the inhibition of further hepatocyte proliferation,
hypothesizing possible involvement of cell cycle upregulators and inhibitors. We
studied protein levels in expression of cyclins, cyclin dependent kinases (CDKs)
and CDK inhibitors (CKIs), and their in situ hepatic lobular distributions in
partial hepatectomized rat liver. Cyclin E was expressed 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 play an important role in the inhibition of
further cell division, although still unclear. Constitutively expressed CDK6
decreased after 1 day. p18 showed peak expression within 1 day, and p16, p21,
p27 and p57 were stronger at terminal periods. During the expected period of
their activity, intranuclear translocations were observed in cyclin E, p18 and
p16. There was no evidence of regional distribution in hepatic lobular
architecture, instead, diffuse in situ expression, corroborating synchronous
event, was found.