THE UPTAKE OF GUANINE, URACIL, LYSINE AND GLYCINE BY ASCITES CELLS PRETREATED WITH AZASERINE AND 6-THIOGUANINE

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Abstract
In S180 ascites cells pretreated with 6-thioguanine, uptake of label from [14c]guanine or [14c]uracil into nuclear RNA and soluble RNA (s-RNA) proceeds at the normal rate. However, particularly with [14c]uracil, the label appears at a decreased rate in microsomal RNA. The uptake of [14C]uracil label into DNA in such cells is decreased to 50% of normal. Pretreatment of cells with azaserine results in a decreased uptake of L-[14C]lysine, and in increased uptake of [14C] guanine and [14C]uracil. Pretreatment of cells with a combination of both drugs results in an almost complete inhibition of the appearance of [14C] uracil label in DNA, and an 85% decrease in the uptake of L-[14C] lysine into microsomal protein. It is suggested that in cells treated with 6-thioguanine (either alone or in combination with azaserine) there is a defect in the ability of microsomal RNA to accept amino acids and nucleotides transported by s-RNA.