Representative data showing the effect of collagen on platelet aggregation and HSP27 phosphorylation (Ser-78) in platelets in patients after rivaroxaban administration.

PRP was stimulated by various doses of collagen for 5 min, and the reaction was terminated by the addition of ice-cold EDTA (10 mM) solution. The black line indicates the percentage of transmittance of each sample (PRP recorded as 0%, and PPP was recorded as 100%). The blue line indicates small aggregates (9–25 μm); the green line, medium aggregates (25–50 μm); the red line, large aggregates (50–70 μm). The distributions (%) of aggregated particle size were measured by AUC of each particle size. The lysates of platelets were subjected to Western blot analysis using antibodies against HSP27, or phospho-specific HSP27 (Ser-78). Representative results obtained from five patients before rivaroxaban administration (A) and after the administration for 2 days (B). In the lower panel, the histogram shows quantitative representation of the collagen-induced phosphorylation levels obtained from laser densitometric analysis. The levels are expressed as the fold increase to the basal levels presented as lane 1. Each value represents the mean ± SEM. *p