A modified Langendorff technique for metabolic investigations.

A small amount of fluid keeps dripping from the apex of the isolated, perfused heart, after cannulating the pulmonary artery and carefully preventing leakage from caval and pulmonary veins. This fluid has a high absorbance at 280 nm, which points to a high protein content; it shows a fall in glucose, and a rise in lactate concentration almost corresponding with the heart's total glucose uptake and lactate release respectively. The data suggest that a small amount of the perfusion fluid reaches the surface of the heart via the interstitial space.