Epitope-dependent localization of estrogen receptorα, but not -β, in en face arterial endothelium

Rapid, nongenomic effects of 17β-estradiol (E2) in endothelial cells are postulated to arise from membrane-associated estrogen receptors (ERs), which have not been visualized in vascular tissue. To identify membrane ERs, we used multiple site-directed ERα or ERβ antibodies to label en face rat cerebral and coronary arterial endothelia. Western blots revealed a novel 55-kDa ERα isoform. Three-dimensional images of cells labeled with these antibodies and markers for the nucleus and caveolin-1 were acquired with a wide-field microscope, deconvolved, and numerically analyzed. We found ERα in the nucleus and cell periphery, where one-third colocalized with caveolin-1. The receptor location was dependent on the epitope of the antibody. Human ovarian surface epithelium produced similar results; but in rat myometrium, the distribution was epitope independent and nuclear. ERβ distribution was predominately intranuclear and epitope independent. A small amount of ERα colocalized with ERβ within the nucleus. The resu...