Effects of dextran on microvascular ischemia-reperfusion injury in striated muscle.

The objectives of this study were 1) to elucidate the effects of dextran (Dx) at a nonhemodiluting dose of 5 mg/kg on ischemia-reperfusion injury in striated muscle and 2) to investigate whether the effects are dependent on the molecular weight of Dx. We used the model of a 4-h pressure-induced ischemia in the hamster skinfold chamber. By means of intravital microscopy the following parameters were assessed: vessel diameter, red blood cell velocity, rolling and adherent leukocytes, macromolecular extravasation, and functional capillary density. The animals received a continuous infusion (total dose 5 mg/kg) of dextran of different molecular weights or equivalent volumes of saline. Seven groups were studied: NaCl (control, n = 6), Dx 1 (n = 6), Dx 40 (n = 7), Dx 60 (n = 6), Dx 70 (n = 7), Dx 110 (n = 7), and Dx 150 (n = 7). Leukocyte rolling was reduced by all Dx fractions, the difference from the control reaching significance 0.5 h after reperfusion in the Dx 60, Dx 70, and Dx 110 group, whereas leukocyte adherence was attenuated by > 40,000-mol-wt Dx at 0.5 h after reperfusion. Concomitantly, functional capillary density tended to improve after treatment with > or = 40,000-mol-wt Dx. However, all Dx fractions studied failed to reduce postischemic macromolecular extravasation. These results provide evidence that Dx at 5 mg/kg attenuates postischemic microvascular disturbances; this effect is molecular weight dependent.