Coronary artery and cultured aortic smooth muscle cells express mRNA for both the classical estrogen receptor and the newly described estrogen receptor beta

Estrogens exhibit potent anti-atherogenic effects through mechanisms which may involve direct effects on the artery. The existence of the classical estrogen receptor (ERalpha) in vascular tissues has been established. Recently a new estrogen receptor (ERbeta) has been discovered which represents a distinct gene product with homology to the classical ERalpha. The purpose of the present study was to determine if ERbeta mRNA is expressed in vascular tissues of female and male primates. Oligonucleotide primers were developed for the specific RT-PCR amplification of ERalpha or ERbeta mRNA. RT-PCR products of the appropriate size for ERalpha and for ERbeta were observed after amplification of RNA isolated from coronary arteries of both male and female cynomolgus monkeys. Similar results were obtained from cultured aortic smooth muscle cells and from monkey reproductive tissues such as ovary and uterus. The relative expression of ERbeta to ERalpha mRNA was greatest in ovary, on the same order of magnitude in monkey vascular tissues and uterus, while the human breast cancer cell line MCF-7 exhibited a very low level of ERbeta relative to ERalpha. Sequence analysis of isolated RT-PCR products showed >95% similarity between the monkey and the published human sequences for both ERalpha and ERbeta. These findings suggest that estrogen may influence vascular gene expression not only through classical ERalpha but also through the newly described ERbeta. These findings also demonstrate the potential for targeting of these receptors in males for prevention or treatment of heart disease.