Expression, distribution and regulation of sex steroid hormone receptors in mouse heart.

The effects of sex hormones on the heart are dependent on the presence and distribution of sex steroid hormone receptors (SSHR) in cardiac tissue. This study used subcellular fractionation, Western blot analysis and densitometry to characterize the subcellular distribution and abundance of estrogen receptor (ER) alpha, ERbeta and androgen receptor (AR) in atrial and ventricular tissue from male and female mice. The results showed that in both atrial and ventricular tissue ERalpha was primarily found in the sarcolemma, whereas ERbeta and AR were predominantly located in the nucleus and cytosol. Interestingly, ERalpha expression was greater in the ventricles compared to the atria, whereas ERbeta and AR expression were similar in both heart chambers. Furthermore, the distribution and abundance of SSHR in the atria and ventricles did not differ between sexes. This study also showed that a reduction in hormone levels (as a result of ovariectomy) resulted in a significant increase in the abundance of ERalpha in the ventricular sarcolemmal fraction. Overall, the results suggest ERalpha, ERbeta and AR distribution and expression are not sex dependent in the mouse heart. However, it appears that ERalpha expression is chamber specific and that, in certain cases, hormone levels can modulate the subcellular location of SSHRs.