[Mechanism of action of biogenic chloramines and hypochlorite on initial aggregation of blood platelets].

The antiaggregant action of two reactive oxidants N,N-dichlorotaurine (chloramine of biogenic type) and sodium hypochlorite on the initial ADP-induced aggregation of rabbit blood platelets has been studied. Platelet aggregation in the reconstructed platelet-rich plasma (PRP) was measured by the nephelometric method, and the aggregation index was an increase in the intensity of small-angle light scattering. The introduction of chloramine at comparatively small concentrations (no greater than 1 mM active chlorine) directly into the reconstructed platelet-rich plasma induces the suppression of the initial aggregation (formation of small aggregates) several times stronger than in the case of its preliminary incubation with plasma alone. This suggests that N,N-dichlorotaurine exerts its antiaggeregant action on the platelet-rich plasma by direct interaction with cells. The effects of the inhibition of platelet aggregation in two variants of introduction of high concentrations of N,N-dichlorotaurine do not significantly differ. In this case a great amount of residual chloramine remains in the plasma, which just induces the suppression of platelet aggregation during subsequent reconstruction of the platelet-rich plasma. Similar data have been obtained in the study of the antiaggregant action of hypochlorite. N,N-Dichlorotaurine and hypochlorite at final concentrations of 0.2-0.3 and 0.15 mM, respectively, inhibit strongly the initial aggregation of isolated platelets (approximately 2 x 10(8) cells in 1 ml) preliminarily activated for 1.5 min by the addition of 100-500 nM ADP. However, the antiaggregants show a more profound suppression of aggregation of unstimulated platelets. The antiaggregant effects of N,N-dichlorotaurine and hypochlorite are probably due to the oxidative modification of sulfur-containing groups in platelet plasmatic membrane.