Differential effects of exercise and heat stress on liver hsp70
accumulation with aging.
Kregel, Kevin C., and Pope L. Moseley.
Departments of Exercise Science and Internal Medicine, The
University of Iowa, Iowa City, Iowa 52242
APStracts 2:0455A, 1995.
Previous reports have suggested that the heat shock response to
passive heating may be blunted by aging. However, during exertional
heating, factors in addition to elevated temperature may amplify the
degree of stress when compared to hyperthermia alone. The purpose of
this study was to compare the pattern of accumulation of the highly
-inducible 72 kDa heat shock protein (HSP72) in liver tissue of mature
(12 mo old) and senescent (24 mo old) male Fischer 344 rats after
either passive or exertional heat stress. A euthermic control group
was exposed to an ambient temperature (Ta) of 25 C for 4.5 hr. A
passive heating (heat) group was exposed to an Ta of 42 C until
colonic temperature (Tco) reached 41 C. An exertional heating
(exercise) group performed intermittent, moderate-intensity treadmill
exercise (similar absolute intensities for the two age groups) at an
Ta of 32 C until Tco reached 41 C. Heating rates were similar in the
heat and exercise groups (0.08 C/min). Rats in both the heat and
exercise groups were maintained at a Tco of 41 C for an additional 30
min and subsequently returned to an Ta of 25 C for 3 hr. Liver HSP72
accumulation was increased in mature rats after both the heat (+192%
vs. control) and exercise (+292%) protocols. In contrast, the
senescent rats demonstrated no significant increase in inducible
HSP70 with heating, but a large increase with exercise (+232%;
p<0.01 compared to control and heat groups). These data suggest
that the blunted heat shock protein response to heating observed with
aging is not a result of the inability to produce inducible HSP72,
since older rats had an robust response to exertional hyperthermia.
Received 1 June 1995; accepted in final form 2 October 1995.
APS Manuscript Number A572-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 November 95