The effect of sesquiterpene lactones on the synthesis of nucleic acid in cultures of human lymphocytes stimulated by phytohemagglutinin.

The investigated sesquiterpene lactones--alatolide, eupatoriopicrine and hydroxyisonobiline, at the concentration 5 microgram/ml, resulted in a complete inhibition of 3H-uridine incorporation into RNA and 3H-thymidine into DNA in cultures of human lymphocytes stimulated by PHA. The blast and mitotic index was close or equal to 0 at this concentration of substances. Susceptibility to the investigated lactones was highest at the initial stage of lymphocyte culture and it gradually decreased with the progression of blastic transformation. At the stage of advanced RNA and DNA synthesis, an addition of the substances to cultures was without any inhibitory effect on the synthesis process.