Induction of 72-kDa heat shock protein does not produce second window of ischemic preconditioning in rat heart
Division of Cardiology, Department of Medicine, Medical College of Virginia, Virginia Commonwealth University, Richmond, Virginia 23298 Ischemic preconditioning (PC) induces delayed phase of protection, known as the second window of protection (SWOP). We investigated this phenomenon in rat and corre...
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Published in | American journal of physiology. Heart and circulatory physiology Vol. 276; no. 1; pp. H224 - H234 |
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Main Authors | , , , , |
Format | Journal Article |
Language | English |
Published |
United States
01.01.1999
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Subjects | |
Online Access | Get full text |
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Summary: | Division of Cardiology, Department of Medicine, Medical College
of Virginia, Virginia Commonwealth University, Richmond, Virginia 23298
Ischemic
preconditioning (PC) induces delayed phase of protection, known as the
second window of protection (SWOP). We investigated this phenomenon in
rat and correlated it with the expression of 72-kDa heat shock protein
(HSP 72). Rats were preconditioned with 1, 2, and 3 cycles of 5-min
left anterior descending artery occlusions, each separated
by a 10-min reperfusion (PC × 1, PC × 2 and PC × 3, respectively). Another group of rats was preconditioned with heat shock
(HS) by raising temperature to 42°C for 15 min. Twenty-four hours
later, rats were given sustained ischemia for 30 min and 90 min
of reperfusion. Infarct sizes (%risk area) were 40.0 ± 7.5, 37.6 ± 5.6, and 47.6 ± 2.4 (mean ± SE) for PC × 1, PC × 2, and PC × 3 hearts, respectively, which were not
different from the sham (49.9 ± 3.9, P > 0.05). In contrast, infarct size
was reduced from 47.5 ± 3.8% in sham to 4.7 ± 2.3%
( P < 0.01) 24 h after HS.
Additionally, early PC significantly reduced infarct size from 47.5 ± 3.8% in controls to 6.0 ± 1.2 and 5.0 ± 1.1% with PC × 1 and PC × 3. Repeated PC cycles induced over a threefold increase in HSP 70 mRNA after 2 h compared with sham
( P < 0.05). HSP 72, which increased
24 h after PC or HS, was not significantly different between the two PC
stimuli. We conclude that PC does not induce SWOP in rat heart despite
enhanced expression of HSP 72. In contrast, HS-induced delayed
protection was associated with enhanced accumulation of HSP 72. It is
possible that SWOP and HS have distinct mechanisms of protection that
may not be exclusively related to HSP 72 expression.
ischemia; stress proteins; infarction |
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ISSN: | 0363-6135 0002-9513 1522-1539 |
DOI: | 10.1152/ajpheart.1999.276.1.H224 |