Expression of oestrogen receptor alpha and beta is higher in skeletal muscle of highly endurance-trained than of moderately active men.

Two known oestrogen receptors (ERs), ERalpha and the recently cloned ERbeta, are expressed in the human skeletal muscle of both males and females. The effects of oestrogen and the role of ERs in skeletal muscle tissue are not well known. Oestrogen receptors and some of their target genes are involved in angiogenic processes. It was hypothesized that ERs are expressed at a higher level in a group with higher oxidative capacity, and that such an enhanced expression would parallel expression of the angiogenic factor -- vascular endothelial growth factor (VEGF).Muscle biopsies were taken from vastus lateralis in 10 highly endurance-trained males and 10 moderately active males and analysed for the expression of ERs and VEGF.The major findings in the present study were the higher mRNA levels of ERalpha, ERbeta and VEGF in the highly endurance-trained than in the moderately active group.These data suggest that the greater mRNA expression of ERalpha and ERbeta and the oestrogen-associated angiogenic factor VEGF support the hypothesis of an involvement of ERs in the adaptation of skeletal muscle to endurance training.