Cold-induced alterations in uncoupling protein and its mrna are
seasonally dependent in ground squirrels.
Nizielski, Steven E., Charles J. Billington, Allen S. Levine.
Neuroendocrine Research Laboratory, VA Medical Center, Minneapolis,
MN 55417 and the Departments of Food Science and Nutrition, Medicine,
Psychology and Surgery, University of Minnesota, Minneapolis-St.
Paul, MN
APStracts 2:0049R, 1995.
We were interested in determining if season affects the ability of
cold exposure to increase brown adipose tissue (BAT) thermogenic
function in 13-lined ground squirrels following acute and chronic
cold (4 C) exposure. Tissues were collected from animals in April and
September following cold exposure for 12, 24 or 48 h. Animals
chronically exposed to the cold (10 d) were killed in early May and
mid-August. We found that mitochondrial uncoupling protein (UCP)
concentrations varied seasonally, concentrations in control animals
(at 23 C) were higher in late-summer (mid-August and September) than
they were in the spring (April and early May). Cold exposure in late
-summer did not induce further increases in UCP concentrations. In
contrast, when animals were cold exposed in the spring, both UCP
concentrations and total UCP increased. Surprisingly, 10 d at 4 C did
not cause a greater increase in UCP concentrations than did 24 h at 4
C. Chronic cold exposure increased the UCP mRNA to [beta]-actin mRNA
ratio 48% in May while a 5 fold increase occurred in August. GDP
binding was increased after 12 h at 4 C in April, in contrast,
animals attempted to hibernate when placed in the cold in September
and no increase in GDP binding was observed. Chronic cold exposure
caused GDP binding to increase at both times of the year. These
results indicate that mitochondrial UCP concen trations are
seasonally regulated in the 13-lined ground squirrel.
Received 23 March 1993; accepted in final form 18 February 1995.
APS Manuscript Number R159-3.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 1 March 1995.