An increase in the activities of glycolytic enzymes in rat lungs produced by nitrogen dioxide

Abstract

Male Jcl: Wistar rats were exposed to 2, 4, and 10 ppm NO₂ for 14, 10, and 7 d, respectively, to examine the effect of NO₂ on the lung glycolytic pathway, a major energy‐generating system in the lung. A highly significant increase in the activities of hexokinase, phosphofructokinase, 3‐phosphoglycerate kinase, pyruvate kinase (PK), and lactate dehydrogenase was observed after 5 d exposure to 10 ppm NO₂, and a significantly higher value was maintained until d 7. Similarly, the activities of all enzymes examined increased significantly by exposure to 4 ppm NO₂, reaching the maximum between 4 and 7 d of exposure, and then approached to near the control levels. The most remarkable increase was found in the PK activity, which reached 1.82‐ (p < 0.001) and 1.53‐fold (p < 0.001) that of the control at d 5 (10 ppm) and d 7 (4 ppm) of exposure, respectively. Upon exposure to 2 ppm NO₂, the PK activity of exposed animals was also increased to 1.23‐fold (p < 0.05) that of the control at d 7, and a higher activity was maintained until d 14.

The glucose‐6‐phosphate dehydrogenase activity of exposed animals increased significantly at d 3, 4, and 14 of exposures to 10, 4, and 2 ppm NO₂, respectively, and a significantly higher value was maintained in the following period of exposure.

These results show that short‐term exposure of rats to 2–10 ppm NO₂ induces the pulmonary systems concerning glycolysis and NADPH‐generation. The generation of energy and NADPH in the lung may be enhanced by NO₂ inhalation.