Fig. 4. Measurements of fluorescence intensity in the mesenteric microcirculation in one representative control and one representative anaphylactic rat. In both animals, normalized signal intensity (SI/S0) curve showed an early decrease because of initial bleaching of the contrast agent (fluorescein isothiocyanate-dextran 70). In the control rat, no subsequent signal intensity increase was observed during the remaining study period, reflecting the absence of fluorescence increase in the interstitium. In contrast, in the anaphylactic rat, the initial signal intensity decrease was followed by a constant and progressive global signal intensity increase, reflecting the increase in fluorescence by leakage of the macromolecular contrast agent in the interstitium.