Age-related peculiarities of breathing regulation and antioxidant enzymes under intermittent hypoxic training

Aging is associated with changes in breathing regulation, particularly, in respiratory sensitivity to hypoxic stimuli. One theory of aging holds that reactive oxygen species play a key role in this process. These species have also been implicated in the carotid body O2 sensing. In the present study we investigated hypoxic ventilatory responses (HVR) and antioxidant enzymes activity in healthy young and elderly people under a 14-day adaptation to intermittent hypoxic training (IHT). The elderly demonstrated decreased HVR and blood catalase (CAT) activity on a background of strong negative correlation between the levels of end-tidal CO(2) tension and superoxide dismutase (SOD) activity. The adaptation to IHT resulted in increased HVR and SOD activity in both groups, and decreased CAT activity in young persons compared with its augmentation in the elderly. Increased SOD activity testifies to an overproduction of reactive oxygen species during IHT. We hypothesize that reactive oxygen species might potentiate a periodical augmentation of cytosolic Ca(2+) in the carotid body. This, in turn, might determine an increase in tyrosine hydroxylase gene expression and promote neurotransmitter synthesis/release, resulting in enhanced HVR. in the carotid body. This, in turn, might determine an increase in tyrosine hydroxylase gene expression and promote neurotransmitter synthesis/release, resulting in enhanced HVR.