The inhibitory effects of horse anti-rat AFP antiserum on the uptake of 2-deoxy-D-glucose by AFP-producing rat hepatoma cells

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Abstract
The inhibitory effect of horse antiserum against rat alpha‐fetoprotein (AFP) on the uptake of 2‐deoxy‐D‐glucose (2dG) by the AFP‐producing rat ascites hepatoma AH66 cells was studied. AH66 cells cultured in medium containing 20% heat‐inactivated antiserum had a 1.5‐fold lower rate of sugar uptake than did AH66 cells which were cultured in medium containing 20% heat inactivated normal horse serum. The inhibition of 2dG uptake by antiserum was dependent on both the concentration and the exposure time of antiserum. Preincubation of AH66 tumor cells for 2 and 6 h with antiserum prior to the measurement of 2dG uptake resulted in a 70.1% and 58.2% decrease in 2dG uptake compared to control cells. Antiserum did not inhibit the rate of phosphorylation of 2dG by tumor cells. Kinetic constants for the uptake of 2dG in both AH66 cells treated with antiserum to AFP and in control cells were calculated from Lineweaver‐Burk plots. The Km remained constant at approximately 1.2 mM, but the Vmax was twice as small for the cells treated with antiserum as for the control cells (571 vs 923 nanomoles/2 × 10s cells/min). These studies suggest that the inhibition of 2dG uptake by treatment with antiserum was the result of a decrease in the number of transport sites, or a decrease in the amount of carrier protein for the sugar which was present on the surface of the plasma membrane of the AH66 cells.