Sodium Pentobarbital Versus α-Chloralose Anesthesia Experimental Production of Substantially Different Slopes in the Transmural CP/ATP Ratios Within the Left Ventricle of the Canine Myocardium

Background Transmural analyses of the creatine phosphate (CP)/ATP ratio in various lamina of the canine myocardium have previously revealed significant variations in the CP/ATP ratio, with the subendocardial layer displaying a decreased ratio relative to the subepicardial layer. Without exception, these results were obtained under sodium pentobarbital anesthesia. These findings have been interpreted to imply that the normal endocardium may be operating in the oxygen-limited domain or that there are transmurally varying set points for the regulation of oxidative phosphorylation. Methods and Results In this work, we examine the effect of the anesthetic regimen on the transmural CP/ATP ratio within the left ventricular wall of the canine myocardium using spatially localized 31P-nuclear magnetic resonance (NMR) and an open-chest model. Two anesthetics were compared, α-chloralose and sodium pentobarbital. Under sodium pentobarbital, the CP/ATP ratio ranged from 1.92±0.06 to 2.51±0.08 from endocardium to epicar...