RNA synthesis and aminoacyl transfer RNA activity of L-2071 cells exposed to dieldrin and DDT

Abstract

In L-2071 tissue culture cells, 50 ppm (50 Μg/ml culture medium) each of dieldrin or DDT reduced total cell count and the rate of14C-leucine incorporation into protein and14C-uridine incorporation into total RNAs; this was the result of an increased rate of14C-uridine incorporation into cytoplasmic soluble and 4S RNA cellular fraction. Total amino acid acceptor activity decreased with dieldrin and DDT treatments, which suggests an actual decrease in functional tRNAs. Dieldrin reduced glutamyl- and aspartyl-tRNA activities whereas phenylalanyl-, tyrosyl-, threonyl-, leucyl-, isoleucyl-, seryl-, and prolyl-tRNA activities decreased with both pesticides. Valyl-, lysyl-, glycyl-, alanyl-, histidyl-, and arginyl-tRNA activities were only slightly changed. The effect of dieldrin was generally greater than that of DDT. In addition, there was degradation of 28S and 18S RNAs to fragments isolated with 4S RNAs. Cells treated with 0.5 and 10 ppm levels of dieldrin demonstrated decreased14C-uridine incorporation into 28S RNAs and increased incorporation into 18S and 4S RNAs after 3 hours and 3 to 6 hours, respectively. Incorporation levels returned to near control levels, thereafter, in whole cell preparations, but remained different from controls when nuclear and cytoplasmic fractions were assessed individually.