IMMINENT ISCHEMIA IN NORMAL AND HYPERTROPHIC LANGENDORFF RAT HEARTS -EFFECTS OF FATTY-ACIDS AND SUPEROXIDE-DISMUTASE MONITORED BY NADH SURFACE FLUORESCENCE

Hypertrophic hearts contain areas of hypoperfusion which can be visual ized by increased NADH surface fluorescence during in vitro perfusion without oxygen-carrying particles under constant pressure and pacing. By contrast, fluorescence remained low when non-hypertrophic hearts we re used instead. When during perfusion of normal hearts the pH of the medium was lowered from 7.5 to 7.0, areas of high fluorescence appeare d in a few minutes. The high fluorescent areas under conditions of car diac hypertrophy or pH 7.0 perfusion could be reduced by addition of s uperoxide dismutase. It indicates that oxygen free radicals interfere with proper flow regulation in areas of low pH. Fluorescence in hypert rophic hearts also diminished during addition of albumin-bound oleate to the standard, glucose-containing, medium. This is in agreement with our earlier finding of fatty acid protection from acidosis-initiated loss of capillary flow (Biochim. Biophys. Acta, 1033 (1990) 214-218). In contrast to low concentrations of free fatty acids, high concentrat ions interfere with tissue oxygenation. This has been illustrated by t he use of 1 mM octanoate, which after a few min caused the appearance of high fluorescent areas. We conclude that decompensation of flow in hypoperfused areas of heart, as occurs in hypertrophy, may be stimulat ed by acidosis and oxygen free radicals.