Effects of ovarian sex hormones and downhill running on fiber-type-specific HSP70 expression in rat soleus

• Published in: Journal of applied physiology (1985) 2009-06, Vol.106 (6), p.2009-2015
• Main Authors: Bombardier, E, Vigna, C, Iqbal, S, Tiidus, P. M, Tupling, A. R
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Estrogens; Estrogens - pharmacology; Exercise; Exercise Test; Female; Fundamental and applied biological sciences. Psychology; Gene expression; HSP70 Heat-Shock Proteins - metabolism; Muscle Fibers, Fast-Twitch - drug effects; Muscle Fibers, Fast-Twitch - metabolism; Muscle Fibers, Fast-Twitch - pathology; Muscle Fibers, Slow-Twitch - drug effects; Muscle Fibers, Slow-Twitch - metabolism; Muscle Fibers, Slow-Twitch - pathology; Muscle, Skeletal - drug effects; Muscle, Skeletal - metabolism; Muscle, Skeletal - pathology; Muscular system; Ovariectomy; Physical Conditioning, Animal; Physiology; Progesterone; Progesterone - pharmacology; Proteins; Rats; Rats, Sprague-Dawley; Rodents
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/japplphysiol.91573.2008

1 Department of Kinesiology, University of Waterloo, and 2 Department of Kinesiology and Physical Education, Wilfrid Laurier University, Waterloo, Ontario, Canada Submitted 4 December 2008 ; accepted in final form 6 April 2009 This study examined the influence of the ovarian sex hormones, estrogen and progesterone, on the fiber-type-specific response of the inducible 70-kDa heat shock protein (HSP70) to damaging exercise in rat soleus. Ovariectomized female rats were divided into three treatment groups ( n = 16 per group): sham (S), progesterone (P; 25 mg pellet), and estrogen (E; 0.25 mg pellet). Each treatment group was divided into control and exercised groups. After 8 days of sham or hormone treatment, animals ran downhill intermittently for 90 min (17 m/min, –13.5° grade) on a treadmill, and soleus muscles were removed 24 h postexercise. HSP70 expression was assessed in whole muscle homogenates by Western blotting and in individual muscle fiber types by immunohistochemical analysis of serial cross sections of soleus samples. Comparisons between control groups showed that HSP70 expression in soleus was increased ( P < 0.05) in E compared with both S and P. No difference ( P > 0.05) was observed between S and P. Following downhill running, HSP70 content in soleus was increased ( P < 0.05) compared with control in S and P, but not ( P > 0.05) in E. As a result, soleus HSP70 content following downhill running was not different ( P > 0.05) between any of the treatment groups. Under all conditions, HSP70 content was higher in type I vs. type II fibers, and the effects of both estrogen and exercise on HSP70 expression in soleus were also more pronounced in type I vs. type II fibers. These results demonstrate that 1 ) estrogen regulates HSP70 expression in skeletal muscle, increasing basal HSP70 expression and preventing further increases in HSP70 in response to exercise; 2 ) progesterone is not involved in the regulation of HSP70 expression in skeletal muscle; and 3 ) the effects of estrogen and exercise on HSP70 expression in skeletal muscle are fiber type specific. estrogen; progesterone; muscle fiber type Address for reprint requests and other correspondence: A. R. Tupling, Dept. of Kinesiology, Univ. of Waterloo, Waterloo, ON, Canada N2L 3G1 (e-mail: rtupling{at}uwaterloo.ca )