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.


CONCLUSIONS
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.
Serebrovskaya
T V
TV
Bogomoletz Institute of Physiology NASU, Kiev, Ukraine. sereb@mail.kar.net
Karaban
I N
IN
Kolesnikova
E E
EE
Mishunina
T M
TM
Swanson
R J
RJ
Beloshitsky
P V
PV
Ilyin
V N
VN
Krasuk
A N
AN
Safronova
O S
OS
Kuzminskaya
L A
LA
D000222:Adaptation, Physiological; D000328:Adult; D000367:Age Factors; D000375:Aging / Q000502:physiology*; D000531:Altitude; D000704:Analysis of Variance; D004295:Dihydroxyphenylalanine / Q000097:blood*; D004298:Dopamine / Q000097:blood*; D005260:Female; D006801:Humans; D000860:Hypoxia / Q000209:etiology / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D011336:Probability; D011659:Pulmonary Gas Exchange; D012016:Reference Values; D012129:Respiratory Function Tests; D012680:Sensitivity and Specificity; D018709:Statistics, Nonparametric
D004295:Dihydroxyphenylalanine; D004298:Dopamine