Biochemical and morphological aspects of nitrogen dioxide toxicity and the effect of ethanol intake

Abstract

Effect of short‐term exposure to 5 ppm of nitrogen dioxide (NO₂) for 3 consecutive days on endogenous rat heart, serum and liver lactate dehydrogenase (LDH) was studied in male rats maintained on water or on 10% ethanol solution as the sole drinking fluid for 10 days preceding and during NO₂ exposure. Animals were pair‐fed. Measurements of hepatic alcohol and aldehyde dehydrogenase were also made. Exposure to NO₂ had little effect on body or liver weights from corresponding controls maintained on water. Ethanol intake increased liver weight in controls and in NO₂‐treated rats. Endogenous heart LDH was significantly increased by the NO₂ exposure compared to water drinking controls. Ethanol intake negated this effect on LDH in NO₂‐exposed animals. Kinetic studies on NO₂‐mediated action on heart LDH indicate higher V_max and apparent K_m values in NO₂‐treated rats than in the corresponding controls, compared to normal values in NO₂‐exposed ethanol drinking rats and their respective controls. No changes occurred in serum or in liver LDH or in hepatic ethanol and acetaldehyde metabolizing enzymes studied as a function of the NO₂ exposure or the ethanol drinking. The results suggest that specific alteration of heart LDH without concomitant changes in serum LDH may reflect an early indication of cardiac injury by NO₂ exposure.

Key words:

• Ethanol
• lactate dehydrogenase
• NO₂