EFFECTS OF ORAL-ADMINISTRATION OF DIFFERENT DOSES OF PURIFIED MICRONIZED FLAVONOID FRACTION ON MICROVASCULAR REACTIVITY AFTER ISCHAEMIA REPERFUSION IN THE HAMSTER-CHEEK POUCH/

1 The effects of a purified micronized flavonoid fraction (S5682) on m ean internal diameter and blood flow of arterioles and venules, as wel l as the functional capillary density (FCD) were evaluated in the hams ter cheek pouch microvasculature before and after 90 min of total isch aemia. 2 Male hamsters were treated for ten days, twice a day, with or al doses of S5682 (5, 20, 80 and 160 mg kg(-1) day(-1)) or placebo (10 % lactose solution). The cheek pouch preparation was placed under an i ntravital microscope coupled to a closed circuit TV system. Local isch aemia was obtained by a cuff mounted around the neck of the everted po uch where it leaves the mouth of the hamster. 3 Measurements were perf ormed before ischaemia, at the onset of reperfusion and 10, 20, 30, 45 and 60 min thereafter. Diameters were measured by means of an image s hearing device. Red blood cell (RBC) velocity was analysed by use of t he dual-slit photometric technique. Blood flow was calculated from dia meters and RBC velocities. FCD, defined as the number of capillaries w ith flowing blood per held of observation, was also assessed. 4 During reperfusion, placebo-treated animals showed a significant vasodilatat ion, a decrease in blood how and FCD and S5682-treated animals showed a clear trend, dose-dependent, towards maintaining these parameters cl oser to the value found before ischaemia. 5 In conclusion, our results indicate that S5682 improves the microvascular reactivity and FCD aft er ischaemia/reperfusion. These data suggest that S5682 could function as an antioxidant, which may explain its beneficial therapeutic effec t in chronic venous insufficiency where oxidative stress is involved i n the pathological mechanism.