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Dehydroepiandrosterone (DHEA) is an adrenal steroid and nutritional supplement that may improve insulin sensitivity. Although steroid hormones classically act by regulating transcription, they may also signal through cell surface receptors to mediate nongenomic actions. Because DHEA may augment insulin sensitivity, we hypothesized that DHEA mimics vascular actions of insulin to acutely activate signaling pathways in endothelium-mediating production of nitric oxide (NO) and endothelin 1 (ET-1). Treatment of bovine aortic endothelial cells with either insulin or DHEA (100 nm, 5 min) stimulated significant increases in NO production (assessed with NO-selective fluorescent dye diaminofluorescein 2). These responses were abolished by pretreatment of cells with l-NAME (nitro-l-arginine methyl ester; NO synthase inhibitor) or wortmannin [phosphatidylinositol (PI) 3-kinase inhibitor]. Under similar conditions …