title: Early stimulation of ATP turnover induced by growth factors. Synergistic effect of EGF and insulin and correlation with DNA synthesis.
abstract: Addition of a mixture of EGF + insulin to quiescent cell cultures synergistically stimulates the cells to reinitiate DNA synthesis and cell division. We have previously demonstrated that this mixture rapidly increases ATP turnover in quiescent cells. The present work shows that each of the two growth factors, EGF and insulin, when added separately to quiescent cells was able to stimulate the phosphorylation of the organic acid-soluble compounds (Po) pool and ATP turnover. The stimulation of ATP turnover was closely correlated with the increase in phosphorylation of the Po pool which suggests that Po labelling reflects the ATP turnover. In many experiments, the synergy between the two growth factors on the early increase in phosphorylation of the Po pool was clearly shown. Doubling the concentration of EGF (12-24 ng/ml) or insulin (50-100 ng/ml) did not increase early stimulation of phosphorylation of the Po pool, whereas simultaneous addition of the two growth factors induced a greater stimulation than that of each growth factor separately added. The augmentation in Po labelling after addition of EGF or insulin alone was transient. The synergistic effect of the two growth factors was more significant when determined 150 or 300 min after growth-factor addition. In our experimental conditions, each of the two growth factors, EGF and insulin, was able to induce a stimulation of DNA synthesis. However, the best stimulatory effect was observed with the mixture of the two which synergistically increased DNA synthesis determined between 6 and 24 h after growth-factor addition. The comparison between DNA replication and Po labelling suggests a correlation between the increase in DNA replication and in the total ATP synthesized in the first 5 h after cell stimulation by growth factors added separately or in combination.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D004261:DNA Replication / Q000187:drug effects*; D004357:Drug Synergism; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D007288:Inosine / Q000378:metabolism; D007328:Insulin / Q000494:pharmacology*; D007700:Kinetics; D051379:Mice; D010710:Phosphates / Q000378:metabolism
chemical_list: D007328:Insulin; D010710:Phosphates; D007288:Inosine; D004815:Epidermal Growth Factor; D000255:Adenosine Triphosphate