Partition coefficients P's of contrast media (CMs) were determined using a simple and accurate method. Diatrizoate (Urografin ^R76%) for ionic CMs and iomeprol (Iomeron^R350) for nonionic CMs were partitioned against n-octanol saturated with water at 25°C and 37°C, by rotating vertically at 50rpm (0.28g) for 24hr. Thereafter, n-octanol phases were repartitioned against the n-octanol-saturated water by the same procedure as described above, i.e., back extraction. Concentrations of the CMs in the water phase were measured using ultraviolet optical absorption with dilution by weight and calibration by density. Side effects of CMs are discussed in relation to P

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We aimed at evaluating the spatial heterogeneity of regional dysoxia and its correlation with microcirculatory flow in the epimyocardiurn of Langendorff-perfused rat hearts. Mitochondrial NADH fluorescent image reflecting the O₂ supply-consumption imbalance was recorded by a CCD video-camera system. The patchy fluorescence pattern appeared and remained almost unchanged during hypoxic perfusion in each hearts. The size of high fluorescence zones was distributed around several hundred microns, comparable with anatomical microvascular unit governed by a precapillary arteriole. The spatial pattern of fluorescence was compared with flow distributions measured by a molecular-tracer digitalradiography. The patterns of the two distributions were similar to each other; the mutual correlation coefficient between regional fluorescence and flow was 0.49 and 0.56 at 100- μ m and 400- μ resolutions, respectively. These identical patchy fluorescence patterns also appeared transiently during repetitive reperfusion periods in each hearts. In high fluorescence zones observed during hypoxia, the fluorescence intensity increased more rapidly due to the flow cessation and returned to the control level more slowly after reperfusion than in the other regions. Time constants of fluorescence intensity change during flow cessation and reperfusion showed a significant inverse correlation (mean r= -0.73, p<0.005). In conclusions, heterogeneity and stable appearance of a regional epimyocardial dysoxic state were significantly related to regional flow at a microcirculatory level.

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