Acute microvascular effects of PAF-acether, as studied by intravital microscopy.
Application of PAF-acether (platelet-activating factor) (final concentration 1-20 nM) to the microcirculation of the hamster cheek pouch resulted in dose-dependent vasoconstriction and an increase in macromolecular permeability, as assessed by leakage of intravascular fluorescein-labelled dextran (Mw 150 000). An increase in adhering leukocytes in venules was only seen with 20 nM PAF-acether. Animals made neutropenic by treatment with antineutrophil serum raised in rabbits showed a reduced leakage response to 20 nM PAF-acether, whereas the leakage induced with 5 nM PAF-acether was unaffected. This indicates that the increase in vascular permeability induced by PAF-acether occurs both as a presumably direct effect independent of polymorphonuclear leukocytes (PMNL), and via an indirect PMNL-dependent mechanism. Intravenous administration of PAF-acether (10 micrograms/kg body weight) to hamsters resulted in rapid and transient thrombocytopenia and leukopenia whereas 1 microgram/kg only affected the leukocytes. These potent microvascular effects of PAF-acether support its proposed role as a mediator of allergic and inflammatory reactions.
D000818:Animals; D002610:Cheek / Q000098:blood supply; D006224:Cricetinae; D005119:Extravasation of Diagnostic and Therapeutic Materials; D007213:Indomethacin / Q000494:pharmacology; D007275:Injections, Intravenous; D008297:Male; D008647:Mesocricetus; D008833:Microcirculation / Q000187:drug effects*; D009503:Neutropenia / Q000139:chemically induced; D010972:Platelet Activating Factor / Q000494:pharmacology*; D014661:Vasoconstriction / Q000187:drug effects
D010972:Platelet Activating Factor; D007213:Indomethacin