Macromolecule permeability of in situ and excised rodent skeletal muscle arterioles and venules


In microvessels, acute inflammation is typified by an increase in leukocyte-endothelial cell interactions, culminating in leukocyte transmigration into the tissue, and increased permeability to water and solutes, resulting in tissue edema. The goal of this study was to establish a method to quantify solute permeability (Ps) changes in microvessels in intact predominantly blood-perfused networks in which leukocyte transmigratory behavior could be precisely described using established paradigms. We used intravital confocal microscopy to measure solute (BSA) flux across microvessel walls, hence Ps. A quantitative fluorescence approach (Huxley VH, Curry FE, and Adamson RH. Am J Physiol Heart Circ Physiol 252: H188–H197, 1987) was adapted to the imaged confocal tissue slice in which the fluorescent source volume and source surface area of the microvessel were restricted to the region of vessel that was contained within the imaged confocal tissue section. Ps measurements were made in intact cremaster muscle microvasculature of anesthetized mice and compared with measurements of Ps made in isolated rat skeletal muscle microvessels. Mouse arteriolar Ps was 9.9 ± 1.1 × 10−7 cm/s (n = 16), which was not different from 8.4 ± 1.3 × 10−7 cm/s (n = 6) in rat arterioles. Values in venules were significantly (P < 0.05) higher: 44.4 ± 7.9 × 10−7 cm/s (n = 14) in mice and 25.0 ± 3.7 × 10−7 cm/s in rats. Convective coupling was estimated to contribute <10% to the measured Ps in both microvessel types and both animal models. We conclude that this approach provides an appropriate quantification of Ps in the intact microvasculature and that arteriolar Ps, while lower than in venules, is nevertheless consistent with arterioles being a significant source of interstitial protein.

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American Journal of Physiology-Heart and Circulatory Physiology