HEM0RRHE0L0GY AND KETANSERIN

Abstract

Red blood cell (RBC) filtration in platelet rich plasma (PRP) and platelet poor plasma (PPP) was equally decreased (p < 0.0001) in 120 patients with acute myocardial infarction (AMI) as compared to a control group. In a double-blind experiment 2 groups of 30 patients with AMI received an acute oral dose of 60 mg of ketanserin, a serotonin (5-HT) antagonist at 5-HT2-receptors, or placebo. Ketanserin treatment improved RBC filtration in PRP with an average increase of 30%. A similar experiment using PPP showed a significant increase of 10%. Filtration of plasma improved after ketanserin treatment in PRP, but not in PPP. Cross-exchange experiments showed the ketanserin-induced improvement of RBC filtration in PRP and PPP to be also plasmadependent. 5-HT in vitro at 10−9M deteriorated RBC filtration in PPP (p < 0.05), and ketanserin in vitro at 10−7M counteracted this phenomenon (p < 0.001). Finally we found that the effect of a subacute treatment with ketanserin on the filtration of RBC Suspensions, enriched with a constant amount of white blood cells (WBC), was more pronounced than on control RBC suspensions of patients with AMI.These results indicate that the impaired RBC filtration, reported in vascular diseases may be dependent on a subtle interaction between platelets, WBC, RBC and plasma. Treatment with ketanserin is capable to interrupt this vicious circle of rheological disturbances at different levels, first of all, by improving RBC deformability, but also by counteracting the platelet mediated effects on RBC and by favourably influencing the physical properties of WBC and so preventing clogging phenomena. Serotonin probably plays a pivotal role in these cascade of events and therapy with ketanserin might be of clinical value in diseases where microcirculatory flow is compromised.