Spatial variation of plasma flow in the oxazolone-stimulated microcirculation

Introduction: In cutaneous lymphocytic inflammation, enhanced regional blood flow is suggested by persistent erythema and warmth. Direct assessment of the microcirculation, however, has been limited by tissue edema and skin thickness. Methods: To assess the microcirculatory adaptations to the epicutaneous antigen oxazolone, we studied the first pass kinetics and microvascular topography of the inflammatory skin microcirculation using a specially adapted epi-illumination intravital microscopy system. The fluorescence intravital videomicroscopy and streaming image acquisition of fluorescein-labeled dextran (similar to500,000 MW) injections were used to assess changes in plasma flow. Results: Direct plasma tracer injections of both the oxazolone-stimulated and control microcirculation demonstrated comparable transit times (leading edge and intensity-weighted peak times) from the carotid artery to the superficial vascular plexus (p > 0.05). In contrast to transit times, continuous infusion of the plasma tracer demonstrated a significant increase in the delivery of the fluorescein-labeled dextran to the oxazolone-stimulated microcirculation. Quantitative morphometry of intravital microscopic images demonstrated a 2.2-fold increase in the mean diameter of vessels in the superficial vascular plexus (p < 0.01). Further, fluorescence intensity mapping indicated that the increase was associated with increased perfusion of focal regions of the superficial vascular plexus (p < 0.001). Conclusions: These results indicate that the oxazolone-stimulated adaptations of the inflammatory microcirculation include both microvascular dilatation and the redistribution of plasma flow.