EFFECTS OF SKIN MAST-CELLS ON BLEEDING-TIME AND COAGULATION ACTIVATION AT THE SITE OF PLATELET PLUG FORMATION

We studied the effects of stimulated skin mast cells on bleeding time and thrombin generation which was measured using prothrombin fragment F1+2 (F1+2) and thrombin-antithrombin-III-complex (TAT). In 10 patient s with urticaria pigmentosa (chronic cutaneous mast cell accumulation) the mean bleeding time was significantly prolonged in wounds made on urticaria pigmentosa lesions vs. normal skin (460 +/- 34 vs. 342 +/- 2 7 s, p = 0.005). In 10 atopic subjects skin incisions were made on pri ck-tested sites 30, 60, 120 and 240 min after administration of an all ergen (acute mast cell stimulation), histamine or vehicle. The mean bl eeding time was significantly prolonged at all time points, being maxi mal at 120 min (60% prolonged) in wounds made on allergen-stimulated s kin areas (p <0.01) compared with histamine or vehicle sites. Administ ration of allergen or histamine lowered the TAT concentration in the b leeding-time blood. Furthermore, TAT and F1+2 levels in the bleeding-t ime blood were lower at 60, 120 and 240 min after allergen or histamin e application in comparison with samples collected at 30 min. We concl ude that skin mast cells can regulate primary hemostasis by prolonging bleeding time and by inhibiting thrombin generation.