[Nucleic acid synthesis in the cells of some ascites tumors induced by change in ionic homeostasis].

The DNA and RNA synthesis was studied in the cells of Ehrlich ascite tumour, lymphoma NK/Ly and carcinoma T.O. was studied under conditions when the Na+/K+ ratio was changed by preincubation in salt media at low temperatures. The incorporation of [3H]thymidine was inhibited at a decrease of the Na+/K+ ratio. The high rate of synthesis was observed only when the cells interacted with K+-free media. Under these conditions some cells which had not incorporated the label induced DNA synthesis. RNA synthesis in lymphoma NK/Ly cells was repressed by about 70% at an increase in K+ concentration (cK) up to 30 mM, followed by a further increase and a subsequent decrease at cK greater than 90 mM. In Ehrlich tumour cells the RNA synthesis was increased 2-fold at an increase in cK from 0 to 30 mM and decreased 3-fold within the concentration range of 30-50 mM. At cK of 50-80 mM it remained constant and showed a further decrease at cK greater than 90 mM. As in the case of DNA synthesis this effect was reversible, i. e. when the cells were transferred to a Na+-rich medium the incorporation of the label rapidly increased and reached its maximum after 30-35 min. Ouabain (2 mM) did not prevent the activation. Actinomycin D (0.05 mkg/ml) inhibited the incorporation of [3H]uridine at any values of Na+/K+. Electrophoresis of RNA isolated from the nuclei and cytoplasm of Ehrlich tumour cells showed that the changes in ionic homeostasis result in the synthesis of new forms of RNA. It is concluded that the distribution of Na+ and K+ in intact cell nuclei is uneven and that monovalent cations can control transcription via the tertiary structure of deoxyribonucleoprotein.