Journal of Applied Physiology, Vol 67, Issue 1 32-38, Copyright © 1989 by American Physiological Society
Effects of hypoxia on metabolic rate of conscious adult cats during cold exposure
H. Gautier, M. Bonora and J. E. Remmers
Laboratoire de Physiologie Respiratoire, Faculte de Medecine, Paris, France.
Oxygen consumption (VO2) and shivering movements were recorded in adult,
conscious cats in a thermoneutral (24-27 degrees C) and in a cold (3-8
degrees C) environment during normoxia, hypoxia, or hyperoxia for 55 min.
In the cold environment, VO2 correlated with shivering index (SI) under
conditions of normoxia or ambient hypoxia (FIO2 = 0.12). During normoxia,
VO2 was 63% higher in the cold than the thermoneutral environment. Ambient
hypoxia acutely reduced VO2 in cold and thermoneutral environments, the
decrement being greater for the former than the latter. Similarly, the
variation in VO2 for unit change in SI was greater in hypoxia than normoxic
conditions, suggesting that hypoxia influenced nonshivering as well as
shivering components of cold-induced VO2. Hypoxia induced by CO (FICO =
0.002) also reduced VO2 and SI, a result that is consistent with previous
results indicating that carotid body chemoreceptors do not mediate the
suppression of shivering by ambient hypoxia. Hyperoxia increased VO2 and SI
in the cold, and the effects of both hypoxia and hyperoxia in the cold were
antagonized by increasing FICO2 to 0.03. The results demonstrate that
hypoxia suppresses VO2 in the cold by reducing the intensity of shivering
and, probably, by an action on metabolic rate that is unrelated to
cold-induced calorigenesis.
