Regulation of an aspartyl-tRNA species in BHK cells in culture and in solid tumor form. II. The effect of different sera on aspartyl-tRNA in culture.

In normal tissues aspartyl tRNA is present in 3 separable components by RPC-5-chromatography, 2 small and early eluting peaks and a major component designated rRNAAspIII. A late eluting peak, tRNAAspIV has also been found in many tumors of human and animals origin, and in BHK 21/13 cells grown in culture, where 27% or more of the total aspartate acceptance occurs in this peak. In contrast, normal tissue studied, i.e., hamster liver or kidney, exhibits less than 2.0% of the total aspartyl tRNA as the late eluting tRNAAspIV. Increasing the level of fetal calf serum in the medium from 5 to 15% resulted in a change from 0.79 to 1.83 in the ratio of tRNAAspIII--tRNAAspIV in BHK cells. Utilizing sera from different species, the percentage of tRNAAspIV was found to vary between 26.8 and 66.0% while the combined percentages of tRNAAspIII and tRNAAspIV varied between 59.5 and 80.8%. It appears that the increased tRNAAspIII was derived from tRNAAspIV and vice versa indicating that there may be a close structural relationship between tRNAAspIII and tRNAAspIV. It was also observed that BHK tumor cells or ascitic fluid enhanced the appearance of tRNAAspIV in normal host liver.