Increased microvascular permeability in the hamster cheek pouch induced by oxidized low density lipoprotein (oxLDL) and some fragmented apolipoprotein B proteins.

Objective And Design: Oxidized low-density lipoproteins (oxLDL) and protein fractions obtained by size exclusion chromatography of oxLDL were tested for vascular permeability effects on topical application to the hamster cheek pouch.

Materials: The hamster cheek pouch was prepared for intravital microscopy observations of macromolecular leakage at post capillary venules (=leaks) with FITC-dextran as tracer.

Treatment: OxLDL (0.1 mg/ml), PAF (platelet activation factor, 50-100 nM) and protein fractions of oxLDL (10 microg/ml) were applied topically to hamster cheek pouches.

Results: Application of oxLDL and PAF resulted in reversible increases in the number of leaks. The PAF-antagonist WEB 2170, L-NAME and a beta(2)-adrenoceptor agonist inhibited (P<0.01) almost completely the macromolecular leakage induced with oxLDL or PAF. Protein fractions were found to be more effective than unfractionated oxLDL in inducing plasma leakage as calculated on mg/ml-basis.

Conclusion: Hamster oxLDL is a potent inducer of macromolecular leakage increase in the hamster cheek pouch microcirculation. The principal effect is mediated by PAF-like structures produced by the oxidation of the LDL-particle but oxLDL also contains low molecular weight proteins that could contribute to the overall vascular permeability increasing effect of ox LDL.