Nitrogen dioxide and the erythrocyte redox state

Rapid Elimination of Blood Alcohol Using Erythrocytes: Mathematical Modeling and In Vitro Study

Erythrocytes (RBCs) loaded with alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALD) can metabolize plasma ethanol and acetaldehyde but with low efficiency. We investigated the rate-limiting factors in ethanol oxidation by these enzymes loaded into RBCs. Mathematical modeling and in vitro experiments on human RBCs loaded simultaneously with ADH and ALD (by hypoosmotic dialysis) were performed. The simulation showed that the rate of nicotinamide-adenine dinucleotide (NAD⁺) generation in RBC glycolysis, but not the activities of the loaded enzymes, is the rate-limiting step in external ethanol oxidation. The rate of oxidation could be increased if RBCs are supplemented by NAD⁺ and pyruvate. Our experimental data verified this theoretical conclusion. RBCs loaded with the complete system of ADH, ALD, NAD⁺, and pyruvate metabolized ethanol 20–40 times faster than reported in previous studies. The one-step procedure of hypoosmotic dialysis is the optimal method to encapsulate ADH and ALD in RBCs after cell recovery, encapsulation yield, osmotic resistance, and RBC-indexes. Consequently, transfusion of the RBCs loaded with the complete metabolic system, including ADH, ALD, pyruvate, and NAD⁺ in the patients with alcohol intoxication, may be a promising method for rapid detoxification of blood alcohol based on metabolism.

In vivo effect of nitrogen dioxide on the activities of glycolytic enzymes in red blood cells of rats

The effects of short-term exposure to NO2 on the glycolytic enzymes of rat red cells were examined. Exposure to 10 ppm NO2 resulted in decrease in activities of pyruvate kinase (PK) and phosphofructokinase (PFK) at day 1 and then increased progressively. Exposure to 4 ppm NO2 caused progressive increases in these enzyme activities from the first day. At day 5, the PK and PFK activities of exposed animals became higher than those of controls followed by decreasing to the control level at day 10. Red blood cells were fractionated according to their ages. The specific activities of PK and PFK decreased as red cells became older. 7-day exposure to 4 ppm NO2 resulted in elevation of PK and PFK activities in all red cell subfractions. In addition, the amount of youngest cells decreased concomitant with increases in those of older cells. These findings suggest that NO2 inhalation enhances red cell turnover.

Effects of nitrate and nitrite, chemical intermediates of inhaled nitrogen dioxide, on membrane components of red blood cells of rats

Rat blood was incubated at 37 degrees C for 60 min with either NaNO3 or NaNO2 to examine the relationship between the decrease in the hexose content and Ca2+,Mg2+-ATPase activity of red cell membranes, and NO3- and NO2-. The hexose content decreased depending on the NaNO2 concentration up to 100 microM reaching 76% (p less than 0.05) of the control value. NaNO3 had little effect on the hexose content. On the other hand, the Ca2+,Mg2+-ATPase activity decreased depending on the NaNO3 concentration up to 200 microM, where the activity reached 75% (p less than 0.01) of the control value. The effect of NaNO2 on this activity was smaller than that of NaNO3. The sialic acid content and the Na+,K+-ATPase activity did not show significant alterations by incubation with NaNO2 and NaNO3 at below 100 microM. To examine the in vivo effects of NO2- and NO3-, 50 mM NaNO3 was intravenously injected into rats five times at hourly intervals (dose: 1.0 ml/kg body weight), and blood was collected 1 hr after the last injection. The activities of Ca2+,Mg2+- and Na+,K+-ATPases of red cell membranes were decreased to 68% (p less than 0.05) and 80% of the control value, respectively. Reduction by injection of 50 mM NaNO2 was smaller than that by 50 mM NaNO3. The results show that the hexose content and the Ca2+,Mg2+-ATPase activity of red cell membranes were decreased by NO-x that increased in the blood during short-term exposure of rats to NO2.

Effects of nitrogen dioxide on red blood cells of rats: alterations of cell membrane components and populational changes of red blood cells during in vivo exposure to NO2

Male Wistar rats were exposed to 4 ppm NO2 for 10 days in order to examine the relationship between the changes in components of red cell membranes and alterations of erythrocyte population. Na+, K+-ATPase activity of red blood cell membranes of exposed animals showed a significantly higher value than that of the control at the first and fourth days of exposure and then decreased to under the control value at the seventh day. In order to examine changes in erythrocyte population, red blood cells were fractionated into four fractions according to their density using Dextran density centrifugation. The alteration of the percentage of lowest-density cells (fraction IV) of exposed animals was completely consistent with that of Na+,K+-ATPase activity in addition to that of the sialic acid content as described in a previous report (K. Kaya, T. Miura, and K. Kubota (1980). Environ. Res. 23, 397-409.). The percentage of fraction IV was 1.43- (P less than 0.05) and 1.68-fold (P less than 0.01) those of the control at the first and fourth days of exposure, respectively, and then decreased to under the control value at the seventh day. This decrease accompanied increases in the percentages of higher-density cells (fractions I and II). Examination of subfractions of red blood cells showed that Na+,K+-ATPase activity and the sialic acid content of three fractions with lower densities have higher values in exposed animals than in the control 1 day after exposure to NO2. Based on these results, it is concluded that increases in Na+,K+-ATPase activity and the sialic acid content occurring 1 day after exposure to 4 ppm NO2 were caused by elevated levels of these components in three fractions with lower densities as well as by an increase in the percentage of lowest-density cells in the erythrocyte population. It was also suggested that NO2 inhalation accelerated aging of erythrocytes with respect to density. The change in Ca2+,Mg2+-ATPase activity, in addition to that in the hexose content as described in a previous report (Kaya et al., 1980), was different from those in the sialic acid content and Na+,K+-ATPase activity. Ca2+,Mg2+-ATPase activity and the hexose content of exposed animals showed slightly reduced values 1 day after exposure to NO2. In all subfractions of red blood cells these values were slightly lower in exposed animals than in the controls. Therefore, reduction in Ca2+,Mg2+-ATPase activity and the hexose content is not due to changes in erythrocyte population.

Biochemical changes in humans upon exposure to nitrogen dioxide while at rest

The biological response to controlled exposures of nitrogen dioxide (NO2) was studied in 19 human subjects exposed to 0.2 ppm NO2 for 2 hr and compared to 15 control subjects exposed to filtered air for 2 hr. Seven biochemical blood parameters, including glutathione, red blood cell glutathione reductase, 2,3-diphosphoglycerate, methemoglobin, vitamin E, complement C2, and IgA were measured prior to exposure, immediately after exposure, and 22 hr following exposure. The only variable that showed significant change due to NO2 exposure was glutathione. Glutathione is known to protect the erythrocyte from oxidative stress. The increase in glutathione observed upon exposure to NO2 may be a protective reaction of the erythrocyte to meet the oxidative stress.