The Hamster Cheek Pouch Preparation as a Model for Studies of Macromolecular Permeability of the Microvasculature

Abstract

A method for intravital microscopy studies of macromolecular permeability is described. The cheek pouch of an anaesthetized hamster was everted and a single layer preparation was mounted on a microscope stage and dissected during observation with a stereomicroscope at 10–16 times magnification. The cheek pouch preparation was superfused with a buffered electrolyte solution with pH=7.35 at 37°C and with a PO₂<4kPa (<30 mmHg). Fluorescein labelled dextran ω_w,=145000 (FITC-dextran 145) was used as a tracer for permeability.

Sites of microvascular permeability to macromolecules were indicated by extravasation of FITC-dextran 145. Leakage of this tracer from the microcirculation was found to occur at the postcapillary venules only. The number of FITC-dextran leakage sites was used for quantitation of the permeability during intravital observations in untreated control and indomethacin-treated hamsters. The number of leakage sites was significantly increased at 120 min in control hamsters but not until 300 min in the indomethacin-treated hamsters. There was a significant difference in permeability at 120 min in control hamsters as compared to indomethacin-treated. Analysis of PGE₂-activity in pooled samples of exposed cheek pouches at 5 hours showed 20 times higher activity in these pouches when compared to the unexposed pouches. Indomethacin was found to inhibit PGE₂-synthesis and to reduce the number of leaking postcapillary venules. The model allows studies on the dynamics of macromolecular transport in the microvasculature and its relation to other vascular parameters such as vessel diameter and blood flow. It should also be useful for studies of inflammatory and immunological responses in the microcirculation and the pharmacology of small vessel permeability to macromolecules.