In vivo experiments on the model of wound healing showed that thrombin and thrombin receptor agonist TRAP-6 stimulated heparin secretion by mast cells in rat subcutaneous fat: the saturation of mast cells with heparin decreased, while degranulation and granulolysis increased. In vitro studies showed that TRAP-6 caused a dose-dependent release of beta-hexosaminidase from peritoneal mast cells. TRAP-6 also induced heparin release from these cells and inhibition of amidase activity of thrombin. Heparin released from mast cells had low anticoagulant activity. These data suggest that activation of mast cells with thrombin is mediated by PAR-1.