Distinct Expression of Vascular Estrogen Receptor Subtypes in the Thoracic and Abdominal Circulation of Female Rat

Experimental evidence in isolated vessels suggests vasodilator effects of estrogen (E2) and estrogen receptors (ERs); however, clinical evidence and in vivo studies do not often support beneficial vascular effects of E2/ER. We investigated whether the net systemic vascular effects of E2/ER are determined by the relative expression of ER subtypes in various regions of the systemic circulation. Representative blood vessels from the cephalothoracic circulation (thoracic aorta, carotid, and pulmonary artery) and abdominal circulation (abdominal aorta, mesenteric, and renal artery) were isolated form female Sprague‐Dawley rats. The amount of ERα, ERβ, and GPR30 was measured using Western blot analysis and subtype‐specific ER antibody, and the immunoreactive signal was normalized to the house keeping protein actin. ERα demonstrated a measurable immunoreactive band at 64 kDa with relative intensity in abdominal aorta (0.507±0.14) > renal artery (0.391±0.16) > pulmonary artery (0.237±0.10) = mesenteric artery (0.236±0.08) > carotid artery (0.167±0.07) > thoracic aorta (0.0999±0.04). ERβ demonstrated an immunoreactive signal at 55 kDa that was very strong in all vessels, most prominent in thoracic aorta (1.81±0.59), and not significantly different in the other blood vessels tested. In contrast, GPR30 demonstrated a week signal at 50 kDa, and was not significantly different in thoracic aorta (0.346±0.20) as compared to the other blood vessels tested. Thus the female vasculature demonstrates regional differences in the amount of ERα, which could translate into differences in the E2/ERα‐mediated vascular effects in the thoracic and abdominal circulation. ERβ and GPR30 do not demonstrate significant differences in female blood vessels, and may not play a major role in the differences in the vascular response to E2 in isolated vessels and in vivo .