Ultrastructure of the immediate, histamine-mediated microvascular response in human skin with urticaria pigmentosa.
The immediate microvascular response in the skin of adults with urticaria pigmentosa after activation of mast cells was examined with the electron microscope. Mast cell degranulation was activated by gently rubbing the cutaneous lesion, and biopsy material was removed 5 to 10 min following stimulation. Aspects of mast cell degranulation were found in all the samples. Several indications of the effects produced by histamine release upon permeability of the small upper dermal venules were evident: (1) Scattered endothelial contraction, which resulted in alternation of contracted and dilated portions of the endothelial wall. Deep nuclear indentations in the contracted endothelial cells occurred in a proportion of 53%. (2) Marked dilation and congestion of some venules. (3) Randomly distributed interendothelial gaps, with platelets or red blood cells traversing the gap. The open junctions of small diameter were numerous, whereas the large gaps were numerically few. (3) The presence of a dense material consistent with plasma protein beneath and external to the vascular basement membrane. Vessels showing aspects similar to those occurring after mild thermal injury were noticed. The possibility exists that several mediators and mechanisms superimpose during the early histamine-mediated phase of the vascular response in urticaria pigmentosa following activation of mast cells.
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D001485:Basement Membrane / Q000648:ultrastructure; D004727:Endothelium / Q000648:ultrastructure; D006636:Histamine Release; D006801:Humans; D008407:Mast Cells / Q000648:ultrastructure; D008833:Microcirculation / Q000187:drug effects / Q000648:ultrastructure*; D008854:Microscopy, Electron; D012867:Skin / Q000098:blood supply* / Q000648:ultrastructure; D014582:Urticaria Pigmentosa / Q000473:pathology*