Isozymic changes of acid phosphatase and esterase in regenerating rat liver after partial hepatectomy in relation to cell differentiation

Activities and isozyme patterns of acid phosphatase and esterase were studied in rat liver at different intervals after partial hepatectomy to clarify the grade of immaturity of normal regenerating liver cells as a control for the unlimited proliferation of hepatoma cells. Acid phosphatase and esterase activities in the liver were elevated during a 12-hr period after hepatectomy, while their isozyme patterns did not change from those of immature liver. Similar findings were also observed in the liver of sham-operated rats. Eighteen hours after the operation, at the S phase before cell division, the isozyme pattern of these enzymes began to shift from an adult liver-type to an immature one resembling those of the infant liver 3 weeks after birth rather than those of newborn or fetal liver. Two or three days after partial hepatectomy, the isozymes characteristic of an immature liver type were more apparent. Although enzyme activities mostly returned to the normal adult level one week after the operation, the isozyme patterns did not completely return to those of an adult liver. These results indicate that despite the rapid proliferation of liver cells, the grade of cell differentiation of the regenerating liver after partial hepatectomy is much nearer to that of the normal adult liver rather than that of the fetal liver.