AJP - Regulatory, Integrative and Comparative Physiology, Vol 241, Issue 5 357-R361, Copyright © 1981 by American Physiological Society
Capillary supply of skeletal muscles from acclimatized white-footed mice Peromyscus
S. J. Wickler
Winter-acclimatized white-footed mice (Peromyscus leucopus) can increase
their aerobic heat production under cold stress by 70%. The possibility
that changes in microvascular supply might account, in part, for some of
this increased thermogenic capacity was examined in one of the primary
thermogenic tissues, skeletal muscle. Capillaries were stained
histochemically in four hindlimb muscles of freshly captured Peromyscus in
summer and winter. Capillary density, mean fiber area, and mean capillaries
in contact per muscle fiber were obtained from the soleus, plantaris,
gastrocnemius, and semitendinosus. If results from all individual muscles
are combined, mean fiber area is significantly smaller (8%) and mean
capillary density is significantly greater (40%) in winter muscles. The
mean number of capillaries in contact is not different, but the mean ratio
of capillaries in contact per mean fiber area (index of potential
perfusion) is significantly greater (25%) in winter muscles.
