Effect of mechanical work load on the transmural distribution of glucose uptake in the isolated perfused rat heart, studied by regional deoxyglucose trapping.

The applicability of the 2-deoxyglucose tracer method to the study of the transmural distribution of glucose uptake in the left ventricle of the isolated, Langendorff-perfused rat heart was validated for the myocardium. The total 2-deoxy[3H]glucose trapped in the myocardium was proportional to the glucose uptake which was varied by the mechanical work load and availability of other oxidizable substrates. When the mechanical work of the heart was eliminated by K+-induced arrest, the glucose uptake of 2.0 mumol/min per g protein was evenly distributed across the left ventricular wall. In the beating heart, glucose uptake averaged 4.7 mol/min per g protein, and was about 40% higher in the subendocardial layer than in the subepicardium (P less than 0.001). Measurement of the transmural distribution of coronary flow by the microsphere method indicated that there were no areas of underperfusion in the left ventricle. The transmural gradient in glucose uptake probably is caused by uneven distribution of the mechanical work load.