Reproducibility of microvascular permeability responses to successive topical applications of bradykinin in the hamster cheek pouch

Bradykinin increases leakage of macromolecules at postcapillary venules. Whether the same sites respond to repeated applications of bradykinin is not known. Knowledge of this phenomenon is of importance in ascertaining the mechanisms of vascular wall repair in inflammatory processes. We used the hamster cheek pouch preparation, suffused with buffer bicarbonate (pH 7.4). Fluorescein isothiocyanate-dextran 150 injected iv was used as a tracer of macromolecular microvascular transport. An area of cheek pouch representing 0.8 cm² was scanned using epi- and transillumination light microscopy before, during and after bradykinin application. Video recordings of individual fields representing 1 mm² were examined to determine the number of leakage sites present as well as their position in the field. Usually, 20-40 min of suffusion with buffer was sufficient to wash away the effects of any given dose of bradykinin. For fields observed, 85% of the leakage sites induced by the first dose were the same sites induced by the second application of the same dose of bradykinin. Whether or not the same site responds to a subsequent application may depend upon the type of microvascular wall repair which ensues. We propose that (a) relaxation of bradykinin-contracted endothelial cells is a mechanism of microvascular wall repair consistent with those leakage sites which repeatedly respond to bradykinin stimulation, and (b) platelet plugging of interendothelial gaps may have occurred in those leakage sites refractory to subsequent applications of bradykinin.