Superoxide Dismutase Restores Impaired Histamine‐Induced Increase in Venular Macromolecular Efflux During Diabetes Mellitus

The goal of this study was to determine the role of oxygen radicals in impaired histamine-induced increases in venular macromolecular efflux from the hamster cheek pouch. We used intravital fluorescent microscopy and fluorescein isothio-cynate dextran (FITC-dextran; MW = 70 K) to examine macromolecular extravasation from post-capillary venules in nondiabetic and diabetic (2–4 weeks after injection of streptozoticin) hamsters in response to histamine. Increases in extravasation of macromolecules were quantitated by counting venular leaky sites and by calculating clearance (ml/s × 10−6) of FITC-dextran-70 K. In non-diabetic hamsters, superfusion with histamine (1.0 and 5.0 µM) increased venular leaky sites from 0 ± 0 to 17 ± 6 and 35 ± 6 per 0.11 cm2, respectively. In addition, clearance of FITC-dextran-70 K increased during superfusion with histamine. In contrast, superfusion with histamine did not increase the formation of venular leaky sites (0 ± 0) or clearance of FITC-dextran-70 K in diabetic hamsters....