Regulation of NO diffusion to vascular smooth muscle cells through the strategic location of hemoglobin α and cytochrome b5 reductase 3. MEJ, myoendothelial junction; NO3−, nitrate. (Reprinted by permission from Macmillan Publishers, Ltd. Nature. M.T. Gladwin and D.B. Kim-Shapiro. 491:344–345, copyright 2012.)