Effects of estrogen on genioglossus SERCA activity and gene expression

Objectives: To investigate the effects of estrogen on sarcoplasmic reticulum Ca2+-ATPase (SERCA) activity and gene expression of genioglossus (GG) in female rats, and identify the potential protective role of estrogen on genioglossus contractile properties. Methods: 30 female rats were randomly divided into three groups. Groups A and B were ovariectomized and group C served as control. Seven days after surgery, group B received intramuscular injection of 17â-estradiol at a dose of 30µg/kg, three times a week, for 5 weeks. All those rats were sacrificed 6 weeks after surgery, and the genioglossus was removed for analysis. Sarcoplasmic reticulum Ca2+-ATPase activity was measured in muscle homogenates by detecting the amount of inorganic phosphorus ion released in a standard coupled enzyme assay. SERCA mRNA level was observed using a real-time quantitative reverse transcription-polymerase chain reaction (Q-RT-PCR).Results: Compared with group C, there was a marked decrease in SR Ca2+-ATPase activity in group A (P<0.01). Furthermore, SERCA mRNA level was also down regulated in group A (P<0.01).While no prominent differences in SR Ca2+-ATPase activity and SERCA mRNA level existed between group B and group C (P>0.05). Conclusions: Ovariectomy may result in a reduction in SR Ca2+-ATPase activity and SERCA gene expression that is reversed with estrogen replacement. Probably estrogen affects the contractile properties of genioglossal muscle by this way.