Left-hand panels, the gating strategy used to enumerate CD34⁺KDR⁺ cells in healthy men. First, CD34⁺ cells were identified in the ungated white blood cell population. Then the expression of KDR was assayed in the CD34⁺ cell gate in order to identify and quantify CD34⁺KDR⁺ cells (indicated by the oval). Right-hand panel, CD34⁺KDR⁺ cells were lower in men with high testosterone and low E2 compared with subjects with low testosterone and high E2. *P≤0.05. Where not specified, the x- and y-axis represent arbitrary fluorescence units. T, testosterone.