AJP - Regulatory, Integrative and Comparative Physiology, Vol 253, Issue 1 77-R82, Copyright © 1987 by American Physiological Society
Metabolism in lizards: low lactate turnover and advantages of heterothermy
M. Guppy, S. D. Bradshaw, B. Fergusson, I. A. Hansen and C. Atwood
The bobtail lizard (Tiliqua rugosa) encounters environmental temperatures
that range from 7 to 40 degrees C. We have studied the effects of
temperature on the whole-body turnover of glucose, lactate, and fatty acid.
At 35 degrees C turnover rates of glucose and fatty acid account for the
majority of O2 uptake and reflect the low metabolic rate of the bobtail
compared with that of a mammal of equivalent mass. Lactate turnover at rest
is very low. The low rates of lactate production correlate with a lack, or
relative lack, of those tissues that normally produce most of the lactate
in a resting mammal, such as nonnucleated red blood cells, renal medulla,
and smooth muscle associated with blood vessels. Q10 (change in rate with a
10 degrees C change in temperature) values for turnover rates of glucose
and fatty acid increase as temperature decreases. It is concluded that
there is an inverse temperature effect that minimizes fuel usage during
torpor.
