Objective: To investigate the potential influence of RANTES on the expression of membranous and cytoplasmic protease activated receptors (PARs) in P815 mast cells. Methods: P815 mast cells were challenged with different concentrations (0.1,1.0,10.0,100.0 ng/ml) of RANTES. The expression of PAR1,PAR2,PAR3 and PAR4 in the time of 2,6 and 16 h were determined by flow cytometry. Results: RANTES significantly down-regulated the expression of membranous rather than cytoplasmic PAR1,and the potentiated effect was abolished by monoclonal anti-RANTES. Nevertheless,RANTES had no effect on the expression of PAR2,PAR3 and PAR4. Conclusion: RANTES can selectively up-regulate membranous PAR1 expression in P815 mast cells,which reveals a novel immunobiologic profile of RANTES as a potential regulator of mast cells function.