Abstract
Heat acclimation upregulates 72-kDa heat shock protein (HSP72) and predisposes to faster activation of the heat shock response (HSR). This study investigates the role played by β-adrenergic signaling and/or plasma thyroxine level in eliciting these features by using rats undergoing 1) heat acclimation (AC; 34°C, 2 and 30 days); 2) AC with β-adrenergic blockade; 3) AC-maintained euthyroid; 4) hypothyroid; 5) hyperthyroid; and 6) controls. The hsp72 mRNA (RT-PCR) and HSP72 levels (Western blot) were measured before and after heat stress (2 h, 41°C, rectal temperature monitored). β-Adrenergic blockade during AC abolished HSP72 accumulation, without disrupting HSR. Low thyroxine blunted the HSR at posttranscriptional level, whereas thyroxine administration in hyperthyroid and AC-maintained euthyroid rats arrested heat stress-evoked hsp72 transcription. We conclude that β-adrenergic signaling contributes to the high HSP72 level characterizing the AC state. Thyroxine has two opposing effects: 1) direct repressive on rapid hsp72 transcription after heat stress; and 2) indirect stimulatory via β-adrenergic signaling. Low thyroxine could account for diminished HSP72 synthesis via lower heat production and thermoregulatory set point.
Original language | English |
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Pages (from-to) | 107-115 |
Number of pages | 9 |
Journal | Journal of Applied Physiology |
Volume | 93 |
Issue number | 1 |
DOIs | |
State | Published - 2002 |
Keywords
- Heat shock protein
- Heat shock response
- Heat stress
- Heat-acclimatory homeostasis
- Hyperthyroid
- Hypothyroid
- Propranolol
- β-adrenergic receptors