Evidence for estrogen receptor alpha and beta expression in skeletal muscle of pigs

Recent research suggests that estrogen receptors (ERs) are of significance in skeletal muscle function. The aim of the present study was to investigate, whether ER alpha and ER beta are expressed in different porcine skeletal muscles and in satellite cells derived from semimembranosus muscle (SM) at the protein and mRNA level. Immunohistochemistry demonstrated positive staining for ER alpha in the nuclei of skeletal muscle cells, while the ER beta stain showed positive signals in nuclei and cytoplasm of skeletal myofibers and myoblasts derived from satellite cells. Additionally, a weak expression of both ER subtypes was seen in skeletal muscle tissue and SM satellite cells with Western blot analysis. A clear expression of the ER alpha mRNA and a weak expression of the ER beta mRNA was seen in skeletal muscle tissue and SM satellite cell cultures, as determined by reverse transcription (RT)-PCR. The present study shows for the first time that both ER alpha and ER beta are expressed in porcine skeletal muscle, which, consequently, could be considered as a target tissue for estrogens or estrogen-like compounds. However, more detailed studies on the functional impact of both receptor subtypes in skeletal muscle are necessary. The porcine SM satellite cell culture provides a suitable in vitro model to investigate estrogenic effects on pig skeletal muscle.