AJP - Regulatory, Integrative and Comparative Physiology, Vol 241, Issue 3 185-R189, Copyright © 1981 by American Physiological Society
Nonshivering thermogenesis in skeletal muscle of seasonally acclimatized mice, Peromyscus
S. J. Wickler
Nonshivering thermogenesis (NST) is a major contributor to total heat
production capabilities of Peromyscus and the magnitude of the NST response
increases dramatically in winter-acclimatized animals. To directly assess
the contribution from skeletal muscle to this NST, a hindlimb perfusion
system was developed for Peromyscus. Oxygen consumption was then measured
with and without norepinephrine (the mediator of NST) in freshly captured
animals in summer and winter. Norepinephrine (NE) was infused at 0.001,
0.01, and 0.1 micrograms . g hindlimb muscle-1 . min-1. Vascular resistance
(VR), calculated as arterial pressure divided by flow rate, increased
during all NE infusions. At doses of 0.001 and 0.01, VR stabilized after
approximately 10 min, but at 0.1 VR continued to rise. Resting oxygen
consumption was 0.817 +/- 0.037 and 0.805 +/- 0.049 mumol O2 . g-1 . min-1
in summer (n = 8) and winter (n = 7) animals, respectively. There was no
apparent increase in oxygen consumption with any dosage of NE. It appears
that the increase in NST in winter animals is not due to an increased NST
in skeletal muscle.
