INCREASED SERUM LEVELS OF DIPEPTIDYL PEPTIDASE-IV (CD26) IN RATS UNDERGOING LIVER-REGENERATION

Dipeptidyl Peptidase IV (DPP IV; CD26) is a cell surface ectopeptidase that has been shown to alter the binding of hepatocytes to the extracellular matrix (ECM), play a role in lymphocyte proliferation and alter the biological activity of several proteins. During hepatic regeneration, there is obvious alteration in the interaction between hepatocytes and the ECM during a rapid phase of hepatic growth. In addition, there is an upregulation of many hepatic and non-hepatic molecules. Our aim was to determine whether the expression of DPP IV in liver regeneration is consistent with a role in either binding of hepatocytes to ECM or modification of growth factors. To achieve this we have measured serum DPP IV levels and compared the expression of DPP IV at the protein and mRNA levels in regenerating and sham-operated liver and kidney tissue, This study reports elevated serum DPP IV levels during hepatic regeneration. Serum DPP IV enzyme activity and antigen levels were increased up to 10-fold at 48 h after partial hepatectomy, This followed the same time course as the increase in hepatic DNA replication. There was no significant increase in the serum levels of another bile canalicular enzyme, leucine aminopeptidase. Analysis of hepatic and renal tissue during regeneration showed no detectable increases in DPP IV enzyme or mRNA. The lack of a detectable increase in enzyme and mRNA levels in the kidney or liver suggests other sources for serum DPP IV or increased release of soluble DPP IV from the liver. The increase in serum may be part of a response to control the biological activity of molecules that appear in the blood during the regenerative process.