Effect of gradual hypoxia on NADH. A: nNADH as a function of perfusate oxygen percentage for biventricular hearts (▲, n = 4), Langendorff hearts (●, n = 2), and blebbistatin hearts (■, n = 3). Perfusate oxygen concentration when NADH increases 10% of full range (NADH = 0.1; B) and 50% of full range (NADH = 0.5; C) is shown. D: slope of NADH at plateau as described in results. For all bar graphs: blebbistatin hearts (white), Langendorff hearts (gray), and biventricular working (black). *P < 0.05 statistically different from blebbistatin hearts.