Quantitative analysis of heterogenous NADH fluorescence in perfused rat hearts during hypoxia and ischemia

Abstract

Photographic negatives obtained by ultraviolet flash photography of perfused rat hearts have been analysed by computer-aided densitometry. Heterogeneous patterns of NADH fluoresence were obtained either by diminishing oxygen availability to the perfused heart with maintained coronary flow (hypoxia) or by ligitation of a coronary artery (regional ischemia). Digital printed images of selected areas of the heart surface (2.5 × 3.6 mm) were produced using a 6-level grey scale and further subsets chosen for histogram display of frequency versus intensity or point line scans. The data show that the NADH fluorescence level in the central region of a hypoxic area is the same as that in a fully anoxic heart, while remaining aerobic areas in a hypoxic heart remain fully aerobic. Similar conclusions apply to ischemic hearts. A border zone where the NADH fluorescence level is intermediate between fully aerobic and fully anoxic can be readily visualized and quantitated in both hypoxic and ischemic hearts. The width of the border zone (about 0.5 mm) is the same for the epicardium and endocardium. The present technique cannot distinguish between the possibilities (a) that the border zone contains mixtures of aerobic and anoxic cells, or (b) that the cells are hypoxic with functioning but O 2-limited electron transport. In either case, it is evident that the border zone, although relatively small, contains many cells that are less likely to become irreversibly damaged than cells in fully anoxic regions.