Estrogen increases male rat aortic endothelial cell (RAEC) PGI2 release

Estrogen has been proposed as a negative risk factor for development of peripheral vascular disease yet mechanisms of this protection are not known. This study examines the hypothesis that estrogen stimulates rat aortic endothelial cell (RAEC) release of PGI2. Male Sprague-Dawley rat abdominal aortic 1-mm rings were placed on 35 mm matrigel plates, and incubated for 1 week. The cells were transferred to a Primaria 60-mm dish and maintained from passage 3 in RAEC complete media and experiments performed between passages 4-10. Cells were incubated with Krebs-Henseleit buffer (pH 7.4) containing carrier or increasing concentrations of beta-estradiol or testosterone for 60 min. The effluent was analyzed for eicosanoid release of 6-keto-PGF1 alpha (6-keto, PGI2 metabolite), PGE2 and thromboxane B2 (TXB2) by EIA (hormone stimulated-basal). Cells were analyzed for total protein by the Bradford method and for cyclooxygenase-1 (COX-1) and prostacyclin synthase (PS) content by Western blot analysis and densitometry. Testosterone did not alter RAEC 6-keto-PGF1 alpha release, whereas estrogen increased RAEC 6-keto-PGF1 alpha release in a dose-related manner. Estrogen preincubation (10 ng/ml) decreased COX-1 and PS content by 40% suggesting that the estrogen-induced increase in male RAEC PGI2 release was not due to increased synthesis of COX-1 or PS. These data support the hypothesis that estrogen stimulation can increase endogenous male RAEC release of PGI2.