Oncodevelopmental expression of rat placental alkaline phosphatase. Detection in oval cells during liver carcinogenesis.

Oval cells isolated from livers of rats fed a choline-deficient diet containing 0.1% DL-ethionine (CDE) have an alkaline phosphatase (ALKP) isozyme which can be distinguished by its electrophoretic mobility from the enzyme present in parenchymal cells isolated from normal liver or livers of rats fed the CDE diet for 4 weeks. The oval cell ALKP has the same electrophoretic mobility as the enzyme from fetal rat liver and placenta. ALKPs from oval cells, parenchymal cells, and placenta all differ from the intestinal enzyme by their electrophoretic mobility, isoelectric focusing, and the patterns of amino acid inhibition of enzyme activity. Oval cells in preneoplastic livers, fetal hepatocytes, and tumor cells of a primary hepatocellular carcinoma induced by CDE feeding stained with a monoclonal antibody directed against rat placental ALKP. Hepatocytes (in normal or preneoplastic livers) and bile duct cells in normal liver did not stain with the same antibody. Placental ALKP may thus be a useful marker in tracing the origin and fate of oval cells during hepatocarcinogenesis.