Estrogen receptor‐α partially mediates estrogen effect on muscle Hsp70 levels

Abstract

We examined the influence of estrogen receptor –α (ERα) activation on estrogen mediated augmentation of heat shock protein 70 (HSP70) content in skeletal muscle. Ovariectomized female rats were administered either estrogen (EST), an ERα agonist (propyl pyrazole triol, PPT), both (EST+PPT), or a sham and served either as unexercised controls or were run downhill (17 m·min-1, −13.5° grade) for 90 min. At 72 hrs post-exercise, soleus muscles were surgically removed, frozen and sectioned and Hsp70 immunohistochemistry and muscle fibre typing performed. In type I muscle fibres, unexercised EST, PPT and EST+PPT groups exhibited elevated (P<0.05) Hsp70 levels relative to unexercised sham animals with EST and EST+PPT also higher (P<0.05) than PPT. Exercise induced elevations (P<0.05) in Hsp70 concentration relative to unexercised animals in sham and PPT groups to levels equal to resting values in the EST and EST+PPT groups in which exercise induced no further changes in Hsp70. The effects of exercise, EST or PPT were not as clear in other muscle fibre types. Since PPT administration alone succeeded in partially augmenting resting muscle Hsp70 levels relative to the greater effect of EST or EST+PPT, we conclude that the ability of EST to augment resting type I muscle Hsp70 content to levels otherwise induced by exercise is partially mediated by the muscle estrogen α-receptor. Supported by NSERC Discovery grants to PMT & ART