Ozone interaction with rodent lung. II. Effects on oxygen consumption of mitochondria.

Abstract

Abstract In order to examine oxidant effects on lung cellular oxidative metabolism, mitochondrial O 2 consumption (substrate oxidation) was studied in the lungs of O 3 -exposed animals. Male rats (60 to 90-day-old) were exopsed to O 3 either acutely (2 p.p.m. for 8 hours) or subacutely (0.8 p.p.m. for 10 to 20 days). For in vitro experiments suspensions of rat lung homogenates or rat lung mitochondria were exposed to a flow of 10 to 15 p.p.m. O 3 per minute for 20 minutes; both homogenate and mitochondrial preparations absorbed O 3 at a rate of 2.3 to 5.0 p.p.m. per minute (depending upon the amount of tissue). A total of 30 to 40 nmoles O 3 per milligram of protein was absorbed during this period. Subsequent to acute exposures, the rate of O 2 consumption (oxidation of succinate) in lung homogenate or mitochondrial fraction decreased approximately 25 per cent (p 3 exposures, subacute exposures resulted in an augmentation of lung cellular O 2 utilization. As high as 45 per cent (p 2 consumption occurred in homogenates of subacutely exposed rat lungs compared to those of control rat lungs. The specific activity (e.g., succinate oxidase activity per milligram protein) in the isolated mitochondral fraction was only 15 per cent (p