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Decreased Uptake of ¹⁴C-labeled Dicarboxylic Amino Acids in Rapidly Growing Hepatomas¹

Departments of Biochemistry [M. R. K., M. A. L.] and Radiology [F. L. K.], New Jersey Medical School, Newark, New Jersey 07103

In contrast to the increased uptake of amino acids which has been found in many neoplastic cells, we have observed a decrease in the net uptake of [¹⁴C]aspartate and [¹⁴C]glutamate in rapidly growing hepatomas relative to rat host liver. When measured 10 min after s.c. injection, the radioactivity from ¹⁴C-labeled dicarboxylic amino acids was greater in liver than in all other tissues examined (blood, skeletal muscle, heart, spleen, lung, and brain) except kidney, where there was an approximately 2-fold greater uptake of aspartate and 10-fold greater uptake of glutamate. Mean uptakes in the rapidly growing Morris hepatomas 7288CTC and 7777 were 9 to 26% of corresponding values for the host livers. Comparison with uptake of ³H₂O indicated that these low values were not solely due to differences in circulation. Decreased uptake was not accompanied by equivalent decreases in the concentration of aspartate and glutamate in the tumors. There were small changes in the net uptake of these amino acids in the slowly growing hepatoma 7787 and no significant differences in regenerating liver and hepatoma 5123C, a tumor of intermediate growth rate. The net uptake of [¹⁴C]arginine and [¹⁴C]lysine in the hepatomas was similar to that in host livers, except for a 250% increase in uptake of [¹⁴C]lysine in hepatoma 5123C. A decreased uptake of the magnitude seen with dicarboxylic amino acids in rapidly growing hepatomas has not been observed with other amino acids.

¹ Supported by Grant CA-16274 from the National Cancer Institute, NIH.

² To whom requests for reprints should be addressed.

Received 3/17/80. Accepted 8/12/80.