Increase in serum sialyltransferase in tumor-bearing rats: the origin and nature of the increased enzyme.

In rats bearing a solid form of AH-109A hepatoma, serum asialofetuin sialyltransferase activity was significantly increased. In order to identify the source of the increased serum sialyltransferase, the asialofetuin sialyltransferase activities of normal and host liver, tumor, and normal and host serum were studied by phosphocellulose column chromatography. While normal and host (day 17) livers exhibited two peaks, namely, transferases I and II, which were previously shown to be the sialylated and unsialylated species, respectively, of beta-galactoside alpha 2 leads to 6 sialyltransferase, the tumor exhibited a single peak of the enzyme, which was a sialylated species (as was transferase I) but was eluted at a position clearly distinguishable from that of either transferase I or transferase II. Under these conditions, both normal and host (day 17) sera were found to contain transferase I but not the tumor-type enzyme. The results have been interpreted as indicating that in rats with AH-109A, the tumor is not the source of the increased serum sialyltransferase. In these rats as well as in normal rats, serum sialyltransferase appears to originate mainly from the liver, whose sialyltransferase activity was also increased in rats with AH-109A.