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We asked the question, "Can thalassemic erythrocytes play some role in alteration of the hemostatic system?", because clinical examination of thalassemic patients shows symptoms and signs related to alterations in hemostatic and circulatory systems, and thalassemic erythrocytes are different from normal erythrocytes. We obtained one of the answers to the question: The erythrocytes of postsplenectomized patients of beta-thalassemia/HbE disease could stimulate their own platelets to aggregate spontaneously. To know the role of erythrocytes in platelet aggregation, we wanted to examine the effect of thalassemic erythrocytes on the coagulation system by focusing of PF3-like activity of erythrocytes, because PF3-like activity of the ghosts of erythrocytes had been reported. For the study, we tried to develop a technique that was accurate and sensitive enough to detect PF3-like activity of blood. The system we developed was the following: 1) We activated the intrinsic coagulation pathway of commercial standard plasma by ellagic acid. 2) CaCl2, a fixed amount of PF 3 and synthetic thrombin inhibitor MD 805 were added to the reaction mixture. 3) At a fixed time, thrombin activity in the mixture was measured by using S-2238 as a substrate. At full activation of the contact system by ellagic acid, the amount of thrombin formed in a certain time depended on the amount of PF3-like substances such as cephalin, freeze-thawed platelets or ghosts of erythrocytes added to the test system, indicating that PF3-like activity of those substances can be measured by the activity of thrombin generated in a fixed time.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical symptoms related with disturbances of the circulatory system are often observed in beta-thalassemia/hemoglobin E (beta-thal/HbE) patients after splenectomy. Pulmonary thrombosis is one of the important contributing factors. However, the pathogenesis of this phenomenon was not known. Previous studies on platelet functions were controversial as platelet-rich plasma (PRP) was employed for all of the studies. By centrifugation, most of the hyperactive platelets were excluded before platelet aggregation tests were performed. Besides, the role of red cells related to platelet aggregation was not investigated. In this study, a platelet function test was designed to avoid these two handicaps of previous work as mentioned, by using whole blood from 15 normal and 40 beta-thal/HbE patients (15 nonsplenectomized and 25 splenectomized) to study spontaneous platelet aggregation. The principle of the test was to evaluate platelet number in whole blood by electronic platelet counter at time 0 (45 minutes after blood collection) and this number was used as 100% of free unaggregated platelets. Then the same specimen of whole blood was incubated at 37 degrees C with continuous stirring by magnetic stirrer in an aggregometer for 8 minutes; at 1 minute intervals free unaggregated platelets were evaluated and calculated as a percentage of the initial control value. The results indicated increased spontaneous platelet aggregation in whole blood of post-splenectomized beta-thal/HbE patients. The residual free platelet number were 24% at 8 minutes after incubation. Effects of red blood cells on spontaneous platelet aggregation were studied by mixing autologous beta-thal/HbE red cells obtained from splenectomized and non-splenectomized patients with platelet rich plasma.(ABSTRACT TRUNCATED AT 250 WORDS)

In order to elucidate the features of platelet aggregation in whole blood, studies were carried out on human blood. The platelet aggregation reaction was monitored by counting the residual free platelet number with an electronic particle counter (Coulter). Platelets in citrated whole blood were aggregated by a very small amount of collagen which did not aggregate platelets in citrated plasma. Such enhancement was not observed if ADP or epinephrine was used. By addition of isolated erythrocytes to platelet rich plasma, enhancement of the platelet response to collagen was obtained. The erythrocyte membrane stabilizer, Dilazep, abolished the enhancement effect of erythrocytes. Those results indicated that erythrocytes enhanced the platelet response to collagen. Although participation of ADP from the erythrocytes in the enhancement was suggested, the results of ADP determinations on suspensions of erythrocytes indicated that other factors of the erythrocytes might be involved in the enhancement.