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.

Geriatric men at altitude: hypoxic ventilatory sensitivity and blood dopamine changes.

BACKGROUND: Short-term exposure to high-altitude hypoxia increases hypoxic ventilatory sensitivity (HVS) in healthy humans. Dopamine (DA) is the implicated neurotransmitter in carotid body (CB) chemoreceptor response, and the microenvironmental conditions in CB tissue are comparable to blood. Continuous DA infusion affected ventilation in animals and humans. Age-related oscillations in blood DA levels may influence peripheral chemoreflexes. OBJECTIVE: Hypoxic ventilatory responses (HVR) relative to blood DA concentration and its precursor, dihydroxyphenylalanine (DOPA) was measured in young and elderly men during short-term altitude adaptation. METHODS: Nine elderly climbers (group 1:61+/-1.4 years) and 7 young healthy subjects (group 2: 23+/-2 years) were tested at sea level on day 0, on day 3 after passive transport to 2,200 m, and on day 14 after climbing to 4,200 and 5,642 m. RESULTS: Sea level HVR in group 1 was 47% lower than in group 2, accompanied by higher blood DOPA (300%) and DA (37%) content. Initial DA and DOPA concentrations showed a negative correlation with initial HVR but a positive correlation with age. Passive transport to middle altitude (2,200 m) increased HVS, doubling HVR slopes in groups 1 and 2 and producing increased maximum expired minute ventilation during isocapnic rebreathing (29 and 28%, respectively). Day 3 2,200-meter blood DOPA content decreased by 22% in group 1 and increased by 300% in group 2. DA increased in both groups. CONCLUSION: The relationship between HVR and the reciprocal DA and DOPA values seen in both groups is associated with age, producing decreased DA receptor sensitivity and enhanced DA reuptake during adaptation to high altitude.

[Free-radical processes under different conditions of body oxygen allowance]. / Vil'noradykal'ni protsesy za umov riznoho kysnevoho postachannia orhanizmu.

Free radical processes (FRP) in mammalian organism are oxygen-depended. The review is devoted to the analysis of pro- and antioxidant processes in mammalian tissues under different oxygen supply conditions. There are described: sources of free radicals; hyperproduction of FRP under hyperoxia and hyperbaria; the role of free radicals in the adaptation to chronic hypoxia (high altitudes, barochamber, chronic heart and lung diseases); production of active oxygen species during the reoxygenation of preliminarily hypoxic tissues; FRP under intermittent hypoxic training; role of FRP in the chemoreception of oxygen. The special attention is paid to three main factors underlined the FR production in hypoxic conditions: the speed of hypoxia increase, the degree of hypoxia and the time of hypoxic exposure.