Isoproterenol potentiates exercise-induction of Hsp70 in cardiac and skeletal muscle

The response to exercise stress is characterized by an increase in circulat ing catecholamines and rapid synthesis of the inducible member of the 70 kD a family of heat shock proteins (Hsp70). Cell culture studies indicate that Hsp70 expression is influenced by beta-adrenergic receptor intermediates i ncluding cyclic AMP (cAMP) and cAMP dependent protein kinase (PKA). Thus, i n the present investigation, the effect of a beta-adrenergic agonist, isopr oterenol (ISO; 10 mg/kg) and a beta-adrenergic antagonist, nadolol (NAD; 25 mg/kg), on the in vivo expression of Hsp70 in rodent cardiac and skeletal muscle following moderate (MOD; 17 m/min) and exhaustive (EXH; 30 m/min) ex ercise was examined. While ISO alone did not induce Hsp70 synthesis, ISO tr eatment potentiated Hsp70 expression following MOD in the white vastus and heart (395 +/- 29 and 483 +/- 29% greater than control respectively, P < 0. 05). Furthermore, this effect was reversed with combined beta-adrenergic ag onist and antagonist treatment (ISO+NAD) indicating that the isoproterenol induced increase in post-exercise Hsp70 expression was mediated via beta-ad renergic receptor activity. However, there were no differences in Hsp70 lev els among treatment groups following EXH. The failure of NAD to attenuate H sp70 accumulation following EXH suggests that beta-adrenergic receptor acti vity is not the main signal in the induction of Hsp70 following exercise. H sp70 induction was dependent on exercise intensity and ISO administration p rior to MOD resulted in Hsp70 levels similar to those observed following EX H. The results from the present investigation indicate that beta-adrenergic receptor stimulation does not induce Hsp70 synthesis per se, but may be on e factor involved in the complex regulation of the stress response to exerc ise in vivo.