The tissue dilution factor (lambda) for the incorporation of
valine into
proteins in the rat cortex and in two different
tumors, AA
ascites and C6
glioma, was determined from measurements of specific activities in the tissue
acid-soluble and aminoacyl-
tRNA pools and in the plasma. A constant plasma specific activity was achieved by a constant infusion rate of [3H]
valine. The data showed that the lambda for
valine was the same in the cortex as in the
tumors, and the recycling was approximately 36%. There was no difference in the lambda calculated on the basis of the specific activities in the tissue
acid-soluble or aminoacyl-
tRNA pools. The average dilution factor was found to be 0.64+/-0.05. The rate of
valine incorporation into
proteins was on average 3.2+/-0.4 and 4.9+/-0.4 nmol/g/min in the cortex for the groups of rats used in the AA
ascites and C6
glioma experiments, respectively. In the AA
ascites tumor the rate was approximately 41 and 29 nmol/g/min 4 and 7 days after
tumor implantation, respectively, whereas in the C6
glioma the rate was approximately 41 and 72 nmol/g/min 6 and 13 days after inoculation, respectively. The
tumors had, in comparison with the cortex, a significantly greater volume of distribution of
valine. The amounts of valyl-
tRNA were significantly greater in the
tumors as compared with the normal cortex, with the exception of the
glioma 6 days after implantation where the concentration was the same as in the cortex.