Rate of aerobic metabolism and superoxide production rate potential in the nematode Caenorhabditis elegans.

We have monitored oxygen consumption as a measure of the rate of aerobic metabolism during the lifetime of Caenorhabditis elegans. We have also developed a chemiluminescent technique which measures exogenous NADPH-stimulated superoxide anion production by freeze-thawed worms. In this assay light production depends on the combined activities of all of the enzymes involved in superoxide production, both directly and indirectly, thus reflecting their activity levels immediately prior to freeze fixation. We have designated this parameter the superoxide production rate potential. The superoxide production rate potential is controlled by the longevity determining gene age-1 and varies in a life cycle-dependent fashion. The metabolic rate generally follows these fluctuations, but additionally shows specific alterations as a response to environmental factors. Metabolic rate and superoxide production rate potential increase by 1.3- and 3-fold, respectively, in reproducing adults. This increase is not due to the contribution of embryonating eggs, however. Culture conditions have a large effect on metabolic rate, but not on the superoxide production rate potential. The energetic cost of movement, measured as consumed oxygen, is low relative to the costs of maintenance and reproduction. Identical superoxide production rate potentials are scored in paralyzed and motile worms, as would be expected.