Fig. 2. Effect of the IP₃R blockers, TMB-8 and 2-APB, on the response of shark VSM to the ET_BR agonist IRL 1620 in Ca²⁺-free Ringer. (A) Representative tracings of the response of VSM to ET_BR agonist stimulation in the presence or absence of TMB-8 or 2-APB. (B) Both inhibitors block the [Ca²⁺]_i mobilization response by about 70% (^*P<0.01).