The following three parameters were studied in Morris
hepatomas of different growth rates: (a) the specific activity of
guanosine dephosphate (
GDP)-fucose:
glycoprotein fucosyltransferase and
cytidine monophosphate (
CMP)-N-acetylneuraminic acid:
glycoprotein sialyltransferase, (B) the content of
GDP-fucosee and
CMP-N-acetylneuraminic acid, and (c) the activity of
alpha-L-fucosidase and
neuraminidase. Fucosyltrasferase activities were significantly elevated in all
hepatomas investigated. Especially high levels of
enzyme were measured in the rapidly growing
tumors 7777, 66, and 3924A. The increase varied between 2- and 3-fold when compared with the corresponding host liver. Conversely, the activity of the sialytransferase was greatly decreased in all
hepatoma lines with a rapid or intermediate growth rate. In the fast-growing
tumor 9618A2, the activity was reduced to 8%.
GDP-fucose and
CMP-N-acetylneuraminic acid were determined by the
isotope dilution technique. In normal rat liver from Buffalo or ACl rats, the concentration of
GDP-fucose was 6.5+/-0.9 and 9.5+/-1.1nmoles/g, wet weight, respectively. In the fast-growing
hepatomas 3924A and 9121, levels up to 21.5 nmoles/g, wet weight, were found, However, the content of
CMP-N-acetylneuraminic acid in
hepatomas was indluenced to a lesser extent by the degree of differentiation of the
tumor. In the most rapidly growing
tumor, 9618A2, a level of
alpha-L- fucosidase seven times higher than in host liver was determined. Moreover, there existed a correlation bewteen the age of the
hepatoma and
enzyme activity. Within the 2nd week after inoculation,
fucosidase activity increased from 130 to 343 nmoles/hr/mg of
protein.
Neuraminidase was measured in a new linked assay system. The activity of this
enzyme was lowered by 50% or was at least unchanged when compared to the activity in host liver. Our results indicate that specific alterations of
fucose metabolism are a characteristic feature of Morris
hepatomas.