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Nucleotide pools of novikoff rat hepatoma cells growing in suspension culture. IV. Nucleoside transport in cells depleted of nucleotides by treatment with KCN
Author(s) -
Plagemann Peter G. W.,
Erbe John
Publication year - 1973
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.1040810113
Subject(s) - nucleotide , uridine , nucleoside , incubation , biochemistry , uracil , cell culture , intracellular , chemistry , de novo synthesis , microbiology and biotechnology , kinetics , biology , rna , dna , enzyme , genetics , gene , physics , quantum mechanics
Incubation of Novikoff rat hepatoma cells in glucose‐free basal medium containing 2 mM KCN results in a rapid and almost complete loss of uracil and adenine nucleotides. By following the fate of radioactivity from 3 H‐nucleoside pulse‐labeled cells during incubation with KCN it was shown that the nucleotides are degraded to nucleosides and bases which are released into the culture fluid. Depletion of the cells of nucleotides by incubation with KCN allows a direct analysis of the kinetics of uridine transport into the cell, since KCN‐treated cells fail to phosphorylate uridine. Uridine uptake follows normal Michaelis‐Menten kinetics with an apparent K n of about 50 μm at 18°C. Uptake is by facilitated diffusion since it does not require energy and uridine is not transported against a concentration gradient. The effects of KCN are largely prevented by the presence of 10 mM glucose in the medium. They are also rapidly reversed by resuspending the cells in fresh medium without KCN. Upon removal of KCN, the cells rapidly regenerate their nucleotide pools and resume growth at the normal rate.