International Journal of Cell Cloning, Vol 5, 27-34, Copyright © 1987 by AlphaMed Press
Induction of hemoglobin synthesis in K562 cells by carbon dioxide deficiency
BA Farley, BM Ohlsson-Wilhelm and PT Rowley
Proliferation and differentiation are inversely related in many cell
culture systems. The study of inducible systems is facilitated by optimal
growth conditions in order that whatever differentiation is observed may be
attributed to a specific effect of the inducer, rather than to a
nonspecific effect of adverse growth conditions. To investigate the role of
CO2 supply in an inducible system, the K562 human leukemia cell line
inducible for hemoglobin synthesis was studied at 10%, 5% and 1.5% CO2
concentrations. The lower the CO2 concentration, the higher the percentage
of benzidine-positive cells but the slower the growth rate. This increase
in benzidine positivity reflected hemoglobin synthesis as indicated by
incorporation of 3H- leucine into globin chains. If, in addition to
reducing CO2 concentration, the complete medium was replaced by a
bicarbonate-free medium, the percentage of benzidine-positive cells was
further increased and growth further slowed. However, if endogenously
produced CO2 was retained by sealing the culture vessel, these effects were
mitigated. Since addition of ribosides blocked these effects, the mechanism
for these effects appears to be inhibition of riboside biosynthesis due to
the depletion of CO2 as a substrate. The implication of this work is that,
for reproducibility in studies of inducible systems in which reduction of
proliferation may itself increase the probability of differentiation, the
CO2 tension, the bicarbonate concentration in the medium and the rate of
egress of endogenously produced CO2 must be kept constant.
