Aim: To study the effect of 3,6-dimethamidodibenzopyriodonium citrate (I-65) on the cytoplasmic free Ca2+ ([Ca2+]i) concentration in rabbit platelet.
Methods: Measurement of the cytosolic Ca2+ of platelets in vitro by using Quin 2-AM fluorescence technique.
Results: In the presence of CaCl2 1 mmol.L-1, I-65 (10, 20, and 30 mumol.L-1) reduced the rise in [Ca2+]i induced by thrombin and calcimycin from 142 +/- 22 nmol.L-1 and 124 +/- 18 nmol.L-1 to 118 +/- 20, 78 +/- 12, 40 +/- 10 nmol.L-1, respectively and 108 +/- 15, 77 +/- 14, 37 +/- 14 nmol.L-1, respectively. In the presence of egtazic acid 2 mmol.L-1, I-65 (10, 20, and 30 mumol.L-1), reduced the Ca2+ release induced by thrombin from 52 +/- 11 nmol.L-1 to 34 +/- 9, 19 +/- 6, and 11 +/- 5 nmol.L-1, respectively. In addition, I-65 (10, 20, and 30 mumol.L-1) also reduced the Ca2+ influx induced by thrombin from 91 +/- 13 nmol.L-1 to 84 +/- 15, 58 +/- 15, and 28 +/- 19 nmol.L-1, respectively.
Conclusion: I-65 inhibited not only the Ca2+ release, but also the influx of Ca2+ in activation platelet.