Title: Identification of bile canalicular cell surface antigen HAM.4 as dipeptidyl peptidase IV (DPPIV) and characterization of its role in hepatic regeneration after partial hepatectomy in rats.
Abstract: Dipeptidyl peptidase IV (DPPIV) has beenimplicated in the control of cell growth anddifferentiation. A rat hepatocyte membrane antigenrecognized by a monoclonal antibody (HAM.4) has now beenshown to be identical to DPPIV by immunoblot analysisand amino acid sequencing. The amounts of DPPIVimmunoreactive protein and enzymatic activity in serumincreased in a manner independent of de novo proteinsynthesis, and without any biochemical orimmunohistochemical changes in hepatic DPPIV, duringliver regeneration after partial hepatectomy in rats.DPPIV purified from serum by HAM.4 antibody-basedaffinity chromatography lacked the NH2-terminal 36 aminoacids of the membrane-bound enzyme, suggesting thatproteolytic cleavage may mediate the release of DPPIVinto serum. No significant differences in therestoration of liver mass or in hepatic DNA synthesis were apparentbetween DPPIV-deficient and normal rats after partialhepatectomy, suggesting that DPPIV may not be essentialfor hepatic regeneration.