Figure 2.

Brachial artery flow-mediated dilation (FMD) expressed as an absolute value (A, D, and G), as a percentage change from baseline (B, E, and H), and shear rate area under the curve until peak FMD (SR AUC) (C, F, and I) assessed in Protocol 1, Protocol 2, and data from both protocols merged, merged data. Initial FMD responses prior to acute BH₄ supplementation in Protocol 1, Protocol 2, and for the merged data are labeled as placebo/pre BH₄ while 4.5 h after acute BH₄ supplementation (10 mg/kg), FMD responses in Protocol 1, Protocol 2, and the merged data are labeled as post BH₄. Figure 2 sample sizes are 9 (6 M/3F), 12 (8 M/4F), and 21 (14 M/6F) for Protocol 1, Protocol 2, and the merged data, respectively. The effect of BH₄ supplementation, within each protocol, was tested with paired Student’s t test. Data are presented as means ± SE. BH₄, tetrahydrobiopterin.