INCREASED NUMBER OF ACTIVATED MAST-CELLS AT SITES OF ABDOMINAL AORTIC-ANEURYSMS

Mast cells participate in immediate and late phase reactions by secret ing mediators which include vasoactive molecules such as histamine, ki nins and tumor necrosis factor, as well as cytokines and degradative e nzymes. The presence of mast cells was investigated using light and el ectron microscopy in aortic tissue specimens from 22 patients with abd ominal aortic aneurysms and 17 age-matched controls undergoing coronar y artery bypass graft. Mast cells stained metachromatically violet wit h Toluidine blue, suggesting they were connective tissue mast cells. A bout four times more mast cells were identified per unit surface area in abdominal aortic aneurysms than in control thoracic aorta. Moreover , most mast cells in aneurysms appeared to be activated showing differ ent degrees of degranulation. Mast cells may participate in the degene rative changes of the vascular wall.