Interstitial lactate and glucose concentrations of the isolated perfused rat heart before, during and after anoxia

In isolated rat hearts perfused according to the Langendorff technique lactate and glucose concentrations were determined in the interstitial transudate and the venous effluent before, during and after periods of 15 or 30 min anoxia. The interstitial transudate emerged at the surface of the heart as a result of albumin-free perfusion. During normoxic perfusion the interstitial lactate concentration was 0.144 +/- 0.025 mmol/l (n = 6); the venous lactate concentration was 0.033 +/- 0.005 mmol/l. From the interstitial and the mean vascular concentration, together with the lactate release and the glucose uptake, the apparent permeability surface area products (P.S product) were calculated using Fick's law. The apparent P.S products for lactate and glucose were 4.6 and 3.9 ml/(min x g), respectively. During anoxia we measured a four- to sixfold increase of the interstitial lactate concentration. At the end of the anoxic periods the apparent P.S product was two- to threefold higher than during normoxia; the apparent glucose P.S product increased about fourfold. After 15 min anoxia the increases of permeability were completely reversed in the reoxygenation period. However, after a period of 30 min anoxia the apparent P.S products for lactate and glucose remained raised, which means that there was a prolonged or even irreversible increase of capillary permeability. Besides the marked transcapillary concentration difference for lactate, these data show prolonged functional alteration of the capillary wall after 30 min anoxia.