Changes in the expression of lipid-mediated signal-transducing enzymes in the flat liver after partial hepatectomy

Prostaglandins (PGs), metabolites of arachidonic acid, and other lipid medi ators produced by phospholipases C (PLC) and D (PLD) are thought to play im portant roles in hepatocyte proliferation. The present study examined lipid -media:ed signaling in the rat liver after partial hepatectomy (PH). Rats w ere killed 1-48 h after 70% PH and the remaining liver tissue was removed. The mRNA and pro rein levels of some signaling molecules were measured by r everse transcriptase-polymerase chain reaction (RT-PCR) and Western blottin g, respectively. The levels of hepatocyte growth factor (HGF) mRNA showed a biphasic change, peaking 3 h and 9 h after PH. The expression of PLC delta 4 peaked at 12 h, but no significant changes in the expression of PLC beta 1 and PLC gamma 1 were seen after PH. T he enzymes involved in Pt; product ion, namely, the expression of cytosolic PLA, and cyclooxygenase 1 (COX1), remained constant after PH. However, the mRNA of COX2 increased transiently at 3 h, and Western blot analysis showed an increase in COX2 protein at 12 h. The expression of PLD1b peaked at 9 h and PLD1a at 12 h, whereas the ex pression of PLD2 remained consistent for 24 h. These results suggest that t ranscriptional controls map act for PLC delta 4, PLD1a/b, and COX2 during h epatocyte regeneration after PH.