Open AccessA cytokinetic approach to determine the range of O 2 ‐dependence of pyrimidine(deoxy)nucleotide biosynthesis relevant for cell proliferation
Author(s) -
Löffler M.
Publication year - 1992
Publication title -
cell proliferation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.647
H-Index - 74
eISSN - 1365-2184
pISSN - 0960-7722
DOI - 10.1111/j.1365-2184.1992.tb01392.x
Subject(s) - uridine , oxygen tension , biology , biochemistry , rna , pyrimidine , pyrimidine metabolism , biosynthesis , de novo synthesis , dna synthesis , cell growth , nucleotide , deoxyadenosine , microbiology and biotechnology , population , protein biosynthesis , cell , in vitro , dna , chemistry , oxygen , enzyme , purine , demography , organic chemistry , sociology , gene
.In vitro cultured Ehrlich ascites tumour (EAT) cells were used because of the ease of their manipulation under different levels of hypoxia. They were used to clarify further the complex mechanism of oxygen‐dependent cell proliferation. On reducing the oxygen concentration from 20% to lower levels (1–7%) an increase in the length of the population doubling time with concomitant reductions in protein, RNA and DNA content of cultures were observed. The incorporation of [ 14 C]HCO 3 ‐ ‐ into the RNA fraction of cells by de novo biosynthesis of uridine monophosphate (UMP) was reduced proportionally to the microenvironmental O 2 tension. Uptake of this labelled precursor by cells in the presence of N ‐phosphonoacetyl‐L‐aspartate was found to be similarly inhibited. To correlate the reduction of cell growth under hypoxia with the functional pyrimidine supply, hypoxic cells were cultured in the presence of a balanced mixture of deoxynucleosides and/or uridine (100 μ m deoxycyti‐dine, 10 μ deoxyadenosine, 10 μ deoxyguanosine, 100 μ M uridine). Above 3% O 2 in the protective atmosphere, no improvement of growth parameters by the exogenous pyrimidinenucleotide precursors was obtained, whereas these compounds had a positive influence below this level. The increase in cell number was raised to about 60% of that of control cultures (20% O 2 ) irrespective of the oxygen tension. In addition, when above 3% O 2 the incorporation of HCO 3 ‐ ‐ into RNA was comparable to that of controls, indicating that the pyrimidine de novo pathway is not a limiting factor in RNA biosynthesis. In conclusion, whereas at suboptimal O 2 levels (5–7%) no correlation between pyrimidine metabolism and reduction of proliferation rate appears to exist, at low O 2 concentrations (<3%) the rate of orotate/UMP production seems to be an important factor in the growth cessation of EAT cells; at critical O 2 tensions (<1%) the lack of pyrimidine‐deoxynucleosides substantially reduces cell cycle progression.