Action of hydroxyurea and N-carbamoyloxyurea on the cell cycle of Tetrahymena.

Abstract

ABSTRACTAddition of a 50 mm dosage of hydroxyurea (HU) to growing cultures of the cilitate Tetrahymena pyriformis allows cell growth to continue but inhibits DNA synthesis, and inhibits cell division after a 20–30% increase in cell number. Higher concentrations of HU cause cell death. T. pyriformis strain differences exist in sensitivity to HU. No cytotoxicity selective to a specific phase of the cell cycle could be demonstrated.The inhibitory effects of HU are entirely reversed by removal of HU and this procedure can be used to induce cell cycle synchrony. Supplementing HU treated cells with deoxyribonucleosides relieves the inhibitory action of HU.Carbamoyloxyurea (COU) is a reactive intermediate of HU and its action on Tetrahymena appears to be similar to that of HU. Because of this similarity and because COU is more potent than HU we postulate that COU is responsible for the unique properties previously ascribed to HU.