AJP - Regulatory, Integrative and Comparative Physiology, Vol 265, Issue 3 518-R523, Copyright © 1993 by American Physiological Society
Nitric oxide and superoxide in cultured cells: limited production and influence on DNA synthesis
C. Firnhaber and M. E. Murphy
Institut fur Physiologische Chemie I, Universitat Dusseldorf, Germany.
The ability of superoxide (O2-) and NO to influence DNA synthesis, as
estimated by [3H]thymidine incorporation in logarithmically growing cells,
was evaluated in three human cell types: embryonic lung fibroblasts, skin
fibroblasts, and mesangial cells. Nontoxic rates of O2- generation (0.2
nM/min-0.2 microM/min) only slightly stimulated DNA synthesis in mesangial
cells (10-13% increase) and did not affect fibroblast DNA synthesis.
Nontoxic rates of NO generation (0.1-10 microM/min) also had only limited
effects, inhibiting DNA synthesis in lung and skin fibroblasts slightly
(10-20% decrease) but not affecting mesangial cells. In all three cell
types, neither O2- nor NO was generated at high enough endogenous rates to
support an autocrinic regulation of DNA synthesis. This and other lines of
evidence indicate that a reaction between O2- and NO is unlikely to account
for their opposing effects on DNA synthesis.
