Thermoregulatory effects of cyanide and azide in the toad, bufo
marinus.
Branco, Luiz G. S., and Gary M. Malvin.
Cardiopulmonary Physiology Program, Institute for Basic and Applied
Medical Research, The Lovelace Institutes, 2425 Ridgecrest SE,
Albuquerque, NM 87108
APStracts 2:0212R, 1995.
An important adaptation to hypoxia is a regulated reduction in body
temperature (anapyrexia), presumably because it lowers metabolic rate
when oxygen supply is limited. Although this beneficial response
occurs in organisms ranging from protozoans to mammals, little is
known of the cellular mechanisms involved. We showed previously that
inhibition of oxidative phosphorylation mediates hypoxia-induced
anapyrexia in the paramecium. In this study we tested the hypothesis
that inhibition of oxidative phosphorylation also causes anapyrexia
in a vertebrate, Bufo marinus. Body temperature (Tb) in toads was
measured in a thermal gradient 24 h before and 24 h after
administration of either NaCN or NaN3, both inhibitors of oxidative
phosphorylation. Subcutaneous NaCN (0.6 mmol/kg) reduced Tb from
29.1+/-0.8 to 19.6+/-0.6 degrees C (p=0.002). Infusion of NaCN
(0.6[mu]mol/kg) into the 4th ventricle of the brain reduced Tb from
30.0+/-0.9 to 24.8+/-1.2 degrees C (p=0.01). Responses to NaN3 were
similar to the NaCN responses. Control injections, and subcutaneous
injections of 0.6 [mu]mol/kg NaCN and NaN3 had no significant effect
on Tb (p>0.32). Neither NaCN nor NaN3 had significant effects on
arterial PO2, PCO2 or pH at 26 degrees C. These results indicate that
inhibition of oxidative phosphorylation in the central nervous system
leads to the selection of cooler temperatures. Thus, reduced
oxidative phosphorylation within the brain may be an important factor
eliciting hypoxia-induced anapyrexia.
Received 24 April 1995; accepted in final form 19 July 1995.
APS Manuscript Number R249-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 July 1995.