CYTOCHALASIN B : VI. Competitive Inhibition of Nucleoside Transport by Cultured Novikoff Rat Hepatoma Cells

Cytochalasin B competitively inhibits the transport of uridine and thymidine by Novikoff rat hepatoma cells growing in suspension culture with apparent K_i's of 2 and 6 µM, respectively, but has no effect on the intracellular phosphorylation of the nucleosides. Choline transport is not affected by cytochalasin B. Results from pulse-chase experiments indicate that cytochalasin B has no direct effect on the synthesis of RNA, DNA, or uridine diphosphate-sugars. The inhibition of uridine and thymidine incorporation into nucleic acids by cytochalasin B is solely the consequence of the inhibition of nucleoside transport.