EFFECTS OF IN VIVO HYPEROXIA ON ERYTHROCYTES. 1. HEMOLYSIS IN MICE EXPOSED TO HYPERBARIC OXYGENATION

The effect of oxygen tension on the growth and metabolism of WI-38 cells

The effect of oxygen tension on cellular growth and metabolism was studied in actively growing WI-38 cells [greater than 90% labeled nuclei (LN)] grown under atmospheres containing 5% CO2 and various combinations of O2 and N2. Cells grown under a partial pressure of oxygen (PO2) of 7.8 +/- 3.5 mm Hg had a significantly slower growth rate, lower saturation densities and higher rates of glucose consumption and lactate production than did cells grown under a PO2 of 44 +/- 7 mm Hg. There were no significant differences in saturation density or the rates of glucose consumption or lactate production between cells grown under PO2 26 +/- 4 mm Hg, 44 +/- 7 mm Hg, or 134 +/- 11 mm Hg. Population doubling time was slightly prolonged at a PO2 of 134 mm Hg compared to a PO2 of 44 mm Hg. Cells grown under a PO2 of 291 +/- 25 mm Hg showed only 20-30% of the growth rate and 10-20% of the saturation density of cells grown under a PO2 of 134 mm Hg. Despite this reduced growth, cells grown under a PO2 of 291 mm Hg consumed four to six times as much glucose and produced four to six times as much lactate per cell as cells grown at a PO2 of 134 mm Hg. Cells grown under a PO2 of 560 +/- 38 mm Hg attached but did not proliferate. This toxic effect of oxygen on cell proliferation was reversible and was not due to an effect of oxygen on the media.

Superoxide dismutase (erythrocuprein) and free radicals in clinical chemistry

Erythrocuprein (superoxide dismutase) has recently been shown to have an enzymic function towards superoxide anions. The discovery of superoxide dismutase, its mode of action, and estimation are reviewed along with a brief introduction to oxygen activation and free-radical chemistry. The formation, activity, and destruction of oxygen free radicals in white blood cells, red blood cells, and subcellular particles are discussed. (a) The production of superoxide anions by white cells during phagocytosis is thought to be advantageous for the overall bactericidal event. (b) Normal red blood cells generate low levels of superoxide anions. Increased levels of free-radical production could play a significant role in accelerating cell ageing (haemolysis). (c) Subcellular particles produce superoxide anions. These as well as organic peroxides have been implicated in drug hydroxylation reactions involving cytochrome P-450.

Studies of paroxysmal nocturnal hemoglobinuria erythrocytes: increased lysis and lipid peroxide formation by hydrogen peroxide

When paroxysmal nocturnal hemoglobinuria (PNH) erythrocytes were exposed to H(2)O(2) they lysed excessively and formed greater than normal quantities of lipid peroxides when compared to red cells of normal subjects and patients with most types of hematologic disease. It was also shown that lytic sensitivity to acidified serum was related to the enhanced lytic sensitivity to H(2)O(2). If the lipid of PNH cells was first extracted then exposed to ultraviolet radiation more lipid peroxides were formed than in extracts of normal red blood cells. The possible explanations for these findings and their relationship to the PNH hemolytic mechanism are discussed.

Peroxidative hemolysis of red blood cells from patients with abetalipoproteinemia (acanthocytosis)

The effect of peroxidative stress on tissue was studied by exposure of red blood cells (RBC) from patients with abetalipoproteinemia to minute amounts of H(2)O(2)in vitro. Red blood cells from untreated patients showed a marked sensitivity to H(2)O(2), as evidenced by hemolysis and lipid peroxidation (peroxidative hemolysis). The appearance of lipid peroxidation products in sensitive cells after exposure to H(2)O(2) was indicated by 1) increases in the 2-thiobarbituric acid (TBA) reaction of trichloroacetic acid extracts, 2) increases in ultraviolet light absorbency of lipid extracts, and 3) decreases in polyunsaturated fatty acids. These changes were accompanied by a decrease in phosphatidyl ethanolamine and phosphatidyl serine in the RBC lipid extract. Similar lipid changes on exposure to H(2)O(2) were observed in the RBC from vitamin E-deficient rats. Treatment of the patients with d-alpha-tocopherol polyethylene glycol succinate by mouth, or addition of dl-alpha-tocopherol to the incubation medium protected the RBC from peroxidative hemolysis. Tocopherol appears to provide a primary biologic defense against peroxidative hemolysis. The presence of nitrite or carbon monoxide, which produced methemoglobin and carboxyhemoglobin, respectively, inhibited peroxidative changes, suggesting a catalytic role for oxy- or deoxyhemoglobin. Substances that prevented lipid peroxidation also prevented hemolysis; in addition, lipid peroxidation appeared to precede hemolysis. These observations suggested that hemolysis was a consequence of lipid peroxidation.

Hyperbaric Oxygen in Cardiovascular Disease

In summary, hyperbaric oxygenation produces remarkable physiologic increases in oxygen transport to body tissues. However, potential benefit from hyperoxygenation in the treatment of ischemic disease appears dependent upon the presence of a partially intact capillary circulation. Improved means for prevention of oxygen toxicity and better technics of oxygen delivery to specific sites are required, if hyperbaric oxygenation is to fulfill present hopes for therapeutic application.