Thrombin can be released from fibrin clots and induces a wide range or biological effects，including cell proliferation and collagen synthesis，On adjacent cells. Periodontal ligament fibroblasts and gingival fibroblasts are known to express protease-activated receptor (PAR)-1，which mediates the growth and clustering of these cells by thrombin．
Thrombin is a regulator of astrocytic endothelin (ET)-1．We have reported that drug-induced gingival fibroblast proliferation is mediated by ET-1，acting via ETA. In the present study，We investigated whether ET-1 was involved in thrombin-stimulated gingival fibroblast proliferation，using cultured rat gingival fibroblasts (CRGF).
Thrombin，acting via PAR-1，caused cell proliferation. No significant increase in the level of immunoreactive ET-1 was observed in thrombin-treated CRGF compared with the control．However，an increase in the level of preproET-1 mRNA was observed after Thrombin stimulation. Thrombin-induced CRGF proliferation was inhibited by SCH79797 (a PAR1 antagonist) and Bq-123 (an ETA antagonist)，but not by BQ-788 (an ETB antagonist)．These results suggest that thrombin-stimulated CRGF proliferation may be partly mediated by ET-1．
P1K-11
