ARCHIVES
OF BIOCHEMISTRY
AND
BIOPHYSICS
Vol. 295, No. 2, June, pp. 391-396,1992
Inert Gas Enhancement Radical Production
of Superoxide
Stephen R. Thorn Institute for Environmental Medicine, 1 John Morgan Building, Philadelphia,
Received January
University of Pennsylvania, Pennsylvania 19104-6068
Walk,
7,1992
Two free radical generating systems, xanthine oxidase/ hypoxanthine or phenazine methosulfate/NADH, were exposed to air plus He, Nx, or Ar at partial pressures ranging from 0.2 to 6.0 MPa, and the rates of production of superoxide, hydroxyl, singlet Ox, and HzOz were measured. All three inert gases acted similarly to enhance the production of superoxide radicals by facilitating interactions between iron and H202, or O2 and organic radicals. These reactions occurred at quite low gas partial pressures, only 0.28 MPa, and hydrostatic pressures of up to 6.0 MPa had no effect on radical reactions. Enhanced radical production may be the basis for the inhibition of cellular growth mediated by inert gases, o 19~2 Academic and inert gas enhancement of Oa toxicity. Press,
36th Street and Hamilton
Inc.
Chemically inert, or noble, gases have been extremely useful for basic studies of narcosis because they do not undergo covalent bonding in vivo. In the quest to understand this phenomenon, several effects of inert gases have been found that are not consistent with narcotic actions (1). One of these is the ability of inert gases to enhance Oz toxicity. The term inert gas is used in this field to refer to gases not metabolized by animals, and so nitrogen is included although it is not a noble gas. Central nervous system O2 toxicity in animals and humans, manifested by convulsions, occurs at lower O2 partial pressures when there is concurrent exposure to high pressures of inert gases (2-5). With regard to pulmonary function, the beneficial effect of mixing inert gases at relatively low pressures (e.g.,
OF BIOCHEMISTRY
AND
BIOPHYSICS
Vol. 295, No. 2, June, pp. 391-396,1992
Inert Gas Enhancement Radical Production
of Superoxide
Stephen R. Thorn Institute for Environmental Medicine, 1 John Morgan Building, Philadelphia,
Received January
University of Pennsylvania, Pennsylvania 19104-6068
Walk,
7,1992
Two free radical generating systems, xanthine oxidase/ hypoxanthine or phenazine methosulfate/NADH, were exposed to air plus He, Nx, or Ar at partial pressures ranging from 0.2 to 6.0 MPa, and the rates of production of superoxide, hydroxyl, singlet Ox, and HzOz were measured. All three inert gases acted similarly to enhance the production of superoxide radicals by facilitating interactions between iron and H202, or O2 and organic radicals. These reactions occurred at quite low gas partial pressures, only 0.28 MPa, and hydrostatic pressures of up to 6.0 MPa had no effect on radical reactions. Enhanced radical production may be the basis for the inhibition of cellular growth mediated by inert gases, o 19~2 Academic and inert gas enhancement of Oa toxicity. Press,
36th Street and Hamilton
Inc.
Chemically inert, or noble, gases have been extremely useful for basic studies of narcosis because they do not undergo covalent bonding in vivo. In the quest to understand this phenomenon, several effects of inert gases have been found that are not consistent with narcotic actions (1). One of these is the ability of inert gases to enhance Oz toxicity. The term inert gas is used in this field to refer to gases not metabolized by animals, and so nitrogen is included although it is not a noble gas. Central nervous system O2 toxicity in animals and humans, manifested by convulsions, occurs at lower O2 partial pressures when there is concurrent exposure to high pressures of inert gases (2-5). With regard to pulmonary function, the beneficial effect of mixing inert gases at relatively low pressures (e.g.,
