Effect of orotic acid on the mitosis of phytohaemagglutinin stimulated human lymphocytes in culture.

The addition of excess orotic acid to cultures of normal human lymphocytes stimulated with phytohaemagglutinin causes a reduction in the mitotic rate. It is suggested that this is caused by competition for the available 5-phosphoribosyl-1-pyrophosphate in the cell leading to a reduced purine synthesis. The significance of these results with regard to orotic aciduria is discussed.