Submitted on August 14, 2008
Revised on January 9, 2009
Accepted on January 27, 2009
Estrogen receptor (ER)
, ER
and Aromatase knock-out effects on lower limb mass and contractile function in female mice
Marybeth Brown1*, Jie Ning2, J. Andries Ferreira, Jennifer L Bogener1, and Dennis B Lubahn1
1 University of Missouri
2 University of Missouri--Columbia
* To whom correspondence should be addressed. E-mail: brownmb{at}health.missouri.edu.
Estrogen (E2) is reported to regulate skeletal muscle mass and contractile function; whether E2 exerts its effects through estrogen receptor alpha (ER
) or beta (ER
) is unclear. We determined the effect of ER or ER elimination on muscle mass and contractile function in multiple muscles of the lower limb, muscles with different locomotor tasks and proportions of fiber types I and II: soleus (Sol), plantaris (Plan), tibialis anterior (TA), and gastrocnemius (Gast), in mature female mice. To determine E2 elimination effects on muscle we also used Aromatase (Ar) knock-out (KO) and wild type (WT) mice. ER and ArKO body weights were ~10 and 20% higher than WT. Although muscle mass tended to show a commensurate increase in both groups, only the TA was significantly larger in ER (p<0.05). Ratios of muscle mass to body mass revealed significantly lower values for Gast and TA in ArKO mice (p<0.05). Tetanic tension (Po) per calculated anatomical cross-sectional area (aCSA) in ER KO was lower in TA and Gast and higher in Plan than in WT. Lower Po/aCSA in ER KO Gast and TA was also supported histologically by significantly less Po/fiber areas (p<0.05). ArKO mice too had lower Po/aCSA in Gast and TA compared to WT. ER KO and WT mice were comparable in all measures. Our results support the hypothesis that E2 effects on skeletal muscle are mediated in part via the ER but E2 effects may be mediated via more than one mechanism or receptor.
