[Role of adenosine diphosphate in the course of thrombin signal transmission]

To study the effects adenosine diphosphate (ADP) on platelet aggregation and expression of glycoprotein (GP) on the surface of platelet membrane after activation of thrombin receptors, so as to investigate its role in thrombin signal transmission.

Peripheral blood samples were collected from from 10 healthy volunteers. Platelets were extracted. The thrombin receptor activating peptides (TRAP), protease-activated receptor 1 activated peptide (PAR1-AP, SFLLRN, 25 micromol/L) and PAR4-AP (AYPGKF, 250 micromol/L) were added into the suspension of platelets respectively to induce platelet aggregation. In apyrase inhibition test apyrase II was added into the suspension of platelets for 2 hours and then PAR1-AP or PAR4-AP was added respectively to observe the the expression of GPIb and P-selectin with flow cytometry.

Either PAR1 and PAR4 induced platelet aggregation. After apyrase II stimulation the PAR4-AP induced platelet aggregation was not influenced and PAR1-AP induced platelet aggregation was partially inhibited with a reversible aggregation curve. Stimulated by PAR1-AP and PAR4-AP the GPIb decreased firstly and then gradually returned to normal. Apyrase VII have not significant influence on the GPIb expression, but accelerated the return of GPIb to the platelet surface after PAR1 stimulation so that the lowest point was accelerated to 2 min, compared to that of the control group (5 min) and there were significantly differences 10 and 30 min later between these 2 groups (all P < 0.05). The P-selectin expression was remarkably increased 2 min after the PAR1-AP and PAR4-AP induction and peaked 2 min later. Apyrase VII did not significantly influence the P-selectin expression in these 2 activation ways.

ADP plays an important role in the thrombin signal transmission, especially in the PAR1 pathway.