The P450 aromatase inhibitor, anastrazole, reduces testosterone-induced P450 aromatase expression and estradiol production in murine ERα +/+ and ERα −/− male aortic endothelial cells. Aortic endothelial cells isolated from male ERα +/+ and ERα −/− mice were treated with testosterone (100 nM or 1 uM) with or without 100 nM anastrazole for 48 hours. Following treatment, total RNA was isolated and used for qRT-PCR analysis of expression of the P450 aromatase gene. Gene expression levels were normalized to GAPDH and expressed as percent change compared to control (panels A and B). To ascertain the amplification and integrity of the resulting qRT-PCR products, the products were separated on a 2% agarose gel (inset, top panel: P450 aromatase and bottom panel: GAPDH). Cell supernatants were collected following treatment and used for ELISA analysis of estradiol release (panels C and D). Results are expressed as means ± SEM. ** p < 0.01 and * p < 0.05 compared to vehicle control.