DNA and protein synthesis inhibition in Chinese hamster ovary cells by dichlorophenoxyacetic acid.

The effects of the herbicide dichlorophenoxyacetic acid (2,4-D) on DNA and protein synthesis were investigated in chinese hamster ovary cells (CHO) employing two different methods. The results showed that the herbicide affects DNA and protein synthesis depending on the stage of growth and method of treatment. 2,4-D action appears to concentrate the cells mainly in the G1/S boundary of the cell cycle. The effect is expressed as an inhibition of DNA and protein synthesis. This effect was revealed not only by the chemical determination of DNA and protein synthesis but also by experiments using autoradiography, using the labelling index to detect the incorporation of [3H]thymidine into the cells. Labelling of the cell nucleus was reduced markedly when cells treated with 2,4-D were in confluency for 4 days after reaching plateau growth.