Pulmonary O 2 Toxicity: Energy Metabolism and Data Analysis

Abstract

Summary

Comparison of homogenates vs mitochondrial preparations in evaluating in vivo respiration and oxidative phosphorylation in lung from rats exposed to 1.5 ATA O₂ for 24, 27, and 30 hr showed that homogenates from experimentally exposed rats may contain extramitochondrial factors inhibitory to respiration which are washed out in mitochondrial isolation procedures. Thus, the use of homogenates is preferable to isolated mitochondria, since they more nearly reflect in vivo oxidative phosphorylation in pulmonary oxygen toxicity studies.

Intercomparison of methods of expressing lung respiration rates and ATP concentration were made in lung of rat subjected to 1.0 and 1.5 ATA O₂ exposures. Care should be exercised in selecting the means for expressing data. Our results indicate that the preferred method for expressing respiration rates is microliters O₂/milligram mitochondrial protein per minute, and for expressing ATP levels is micromoles ATP/milligram mitochondrial protein, in pulmonary O₂ toxicity studies. Evaluation of metabolic activity requires that accurate determinations of the total lung (or individual lung) weight, and some unit of the lung (preferably the organelle responsible for the activity being studied) be determined, e.g., milligram mitochondrial protein per gram lung.