Cellular pathways of mast cell- and capsaicin-sensitive nerve-evoked ileal submucosal arteriolar dilations.
This study characterized mast cell- and capsaicin-sensitive sensory nerve vasodilator mechanisms regulating submucosal arterioles in the guinea pig ileum. The outside diameter of arterioles in in vitro submucosal preparations from milk-sensitized guinea pigs was monitored using videomicroscopy. Superfusion of the cow's milk protein, beta-lactoglobulin (beta-Lg; 5 microM), evoked large dilations, which became completely desensitized. beta-Lg-evoked dilations were blocked by pyrilamine or NG-monomethyl-L-arginine plus indomethacin but not by TTX. Electron microscopic studies revealed that mast cells, in preparations receiving beta-Lg, demonstrated significant reductions of the dispersed and intact granule areas compared with preparations not exposed to beta-Lg. Paired experiments were conducted to determine if capsaicin-sensitive, nerve-evoked responses involved mast cell degranulation. One preparation received capsaicin (200 nM) followed by beta-Lg (5 microM); the other preparation received the drugs in reverse order. Prior treatment with capsaicin or beta-Lg had no effect on subsequent dilations evoked by the alternate treatment. Electron microscopy showed that nerve-arteriole associations were 10 times closer than nerve-mast cell associations. Mast cell numbers were not increased by milk sensitization. These findings suggest that mast cell- and capsaicin-sensitive nerve-evoked vasodilator mechanisms act independently in a model in which mast cell numbers are not increased.
Atwood
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Department of Biology, Queen's University, Kingston, Ontario, Canada K7L 5G2.
James
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Morris
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Vanner
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D000527:Alprostadil / Q000494:pharmacology; D000818:Animals; D001160:Arterioles / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D001920:Bradykinin / Q000494:pharmacology; D002211:Capsaicin / Q000494:pharmacology*; D002417:Cattle; D011464:Epoprostenol / Q000494:pharmacology; D005512:Food Hypersensitivity; D006168:Guinea Pigs; D007082:Ileum / Q000098:blood supply* / Q000294:innervation; D007213:Indomethacin / Q000494:pharmacology; D007782:Lactoglobulins / Q000494:pharmacology; D008407:Mast Cells / Q000502:physiology*; D018715:Microscopy, Video; D008892:Milk / Q000276:immunology; D009130:Muscle, Smooth / Q000098:blood supply / Q000294:innervation; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D011738:Pyrilamine / Q000494:pharmacology; D012701:Serotonin / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology*; D019323:omega-N-Methylarginine / Q000494:pharmacology
D007782:Lactoglobulins; D019323:omega-N-Methylarginine; D012701:Serotonin; D011464:Epoprostenol; D000527:Alprostadil; D011738:Pyrilamine; D002211:Capsaicin; D001920:Bradykinin; D007213:Indomethacin