The effect of pretreatment with antibodies against PAR-1, PAR-2, and EPCR on APC-induced [Ca²⁺]_i signals. (A) [Ca²⁺]_i was monitored in (i) BECs (thin traces) preincubated with antibodies, (ii) N-19, (iii) H-111, (iv) SAM-11, (v) RCR-252, and (vi) RCR-92 (25 μg/mL) at 37°C for 15 minutes. APC (100 nM) was added at the time indicated by arrows. (B) Relative magnitude of changes in [Ca²⁺]_i in BECs in response to APC in which cells were intact or preincubated with antibodies N-19, H-111, SAM-11, RCR-252, or RCR-92. Bars represent normalized mean values of [Ca²⁺]_i ± SEs in response to APC from 3 identical experiments. Normalization was done between paired experiments in which APC-induced changes in signals in antibody-pretreated BECs were compared with APC-induced [Ca²⁺]_i changes performed in subsequent experiments without antibody preincubation. *P < .01. (C) [Ca²⁺]_i increase in HUVECs in response to APC in which cells were intact or preincubated with monoclonal antibodies ATAP-2, H-103, RCR-252, or RCR-92. Bars indicate mean values of [Ca²⁺]_i amplitudes ± SEs in response to APC from 5 identical experiments. *P < .01.