AJP - Regulatory, Integrative and Comparative Physiology, Vol 260, Issue 6 1229-R1234, Copyright © 1991 by American Physiological Society
Brown fat-specific mitochondrial uncoupling protein in adipose tissues of newborn reindeer
P. Soppela, M. Nieminen, S. Saarela, J. S. Keith, J. N. Morrison, F. Macfarlane and P. Trayhurn
Reindeer Research, Finnish Game and Fisheries Research Institute, Rovaniemi.
Reindeer inhabit a severe arctic or subarctic environment, with the young
born in early spring under adverse weather conditions. The extreme northern
climate imposes a major thermal challenge to the newborn, and in the
present study we have examined fetal, neonatal, and young (from 2 wk before
birth to 16 mo postpartum) semidomesticated reindeer from northern Finland
for the presence of thermogenic brown adipose tissue. Adipose tissues were
removed, mitochondria were prepared, and the proteins were separated by
molecular weight and blotted onto nitrocellulose membranes. The membranes
were then probed for the presence of the 32,000-relative molecular weight
mitochondrial uncoupling protein (UCP) unique to brown fat by use of a
rabbit anti-(ground squirrel UCP) serum. Immunoreactivity at the molecular
weight characteristic of UCP was present in perirenal, abdominal,
inter(pre)scapular, sternal, intralumbar, vertebral, tracheal, inguinal,
and omental-mesenteral adipose tissues of newborn reindeer (0-2 days of
age). No immunoreactivity was detected in coronary adipose tissue. UCP was
found at high levels in interscapular and perirenal adipose tissues of
fetal reindeer at 2 wk before birth. Although the protein was present
during the first few days postpartum, little immunoreactivity was found at
1 mo of age, and none was evident by 2 mo. UCP and its mRNA were also
apparent in perirenal adipose tissue of the newborn of another species of
Cervidae, the red deer. It is concluded, on the basis of the immunologic
identification of UCP, that most adipose tissues of newborn reindeer
represent functional brown fat but that there is a subsequent conversion to
white adipose tissue by the 2nd mo of life.(ABSTRACT TRUNCATED AT 250
WORDS)
