Regulation of estrogen receptor α by estradiol in pregnant and estradiol treated rats

Estrogens play an important role in tissue metabolism through specific regulation of several intracellular pathways. We studied ERα regulation in muscle and adipose tissue from pregnant and estradiol treated rats. In both groups, we identified three different ERα inmunoreactive proteins (80, 67 and 46 kDa) using total protein extracts. Because it has been showed that estrogens are able to promote rapid effects in several cellular models, we looked for three ERα-related proteins at plasma membrane. In skeletal muscle of both groups, we positively identified the three ERα-related isoforms in plasma membrane, but in adipose tissue from pregnant we were not able to identify ERα67, and in estradiol treated animals ERα80 was absent. Taking together, our results showed a tissue-specific regulation of whole-cell ERα-related proteins and ERα located at plasma membrane, which should be involved in non-genomic actions of 17β-estradiol. The role of the three ERα inmunoreactive proteins is unknown, however, seems probably related to rapid activation of signalling pathways.