Estrogen receptors alpha and beta: prevalence of estrogen receptor beta mRNA in human vascular smooth muscle and transcriptional effects

BACKGROUND

Estrogens have vascular effects through the activation of estrogen receptors (ERs). In addition to ERalpha, the first ER to be cloned, a second subtype called ERbeta has recently been discovered.

METHODS AND RESULTS

Using a reverse-transcriptase polymerase chain reaction assay that employs the same primer pair to simultaneously amplify ERalpha and ERbeta transcripts, we found that ERbeta is the ER form that is predominantly expressed in human vascular smooth muscle, particularly in women. The transcriptional effects of the 2 ERs in transfected HeLa cells differed. In response to 17beta-estradiol, ERalpha is a stronger transactivator than ERbeta at low receptor concentrations. However, at higher receptor concentrations, ERalpha activity self-squelches, and ERbeta is a stronger transactivator. Tamoxifen has partial agonist effects with ERalpha but not with ERbeta.

CONCLUSIONS

The protective effects of estrogens in the cardiovascular system of women may be due to the genomic effects of ERbeta in vascular tissue.