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Purpose: This study has been conducted to evaluate the effect of urea on aggregation responses of heat-treated platelets. Materials and methods: The urea was added to platelet-rich plasma (PRP) samples in final concentrations of 50 and 100 mM. PRP samples, with or without exogenous urea, were incubated at 37 °C, 39 °C and 41 °C for 90 min and then were stimulated with adenosine diphosphate (ADP) or epinephrine for measuring of platelet aggregation responses. The average reduction in aggregability of heat-treated samples with reference to mean value obtained for control samples treated at 37 °C was expressed as inhibition percentage. Results: Aggregation responses of the samples treated in the presence of 50 mM and 100 mM urea were significantly less inhibited by hyperthermia treatments compared with those treated without exogenous urea. Conclusion: The results indicate that the inhibitory effect of hyperthermia on platelet aggregation responses could be significantly modulated by urea. [ABSTRACT FROM AUTHOR]

Background: Patients with type 2 diabetes mellitus (T2DM) have accelerated atherosclerosis as a pro thrombotic state that is associated with the platelet activation priming. Platelets, which undergo the continuous mild stimulation, may lose their sensitivity to react to a strong stimulation. The present study aimed to investigate activation responses of platelets to mild and subsequent strong stimulations in patients with T2DM and healthy individuals. Methods: Blood samples, which were taken from 40 patients with T2DM and 35 healthy individuals, were collected into the citrate containing tubes. The samples were subjected to the soft centrifugation to prepare the platelet rich plasma (PRP). Platelets in PRP samples were treated at a low (1 μM) concentration and then at a high (10 μM) concentration of ADP. Before and after stimulation with different doses of ADP, levels of CD62P expression and formation of platelet micro particles (PMPs) were measured using a flow cytometry method. Results: The platelets from patients with T2DM had higher levels of CD62P expression before any stimulation (P = 0.003) than control samples. Platelets, which underwent the mild stimulation, indicated lower responses to CD62P expression, but higher PMPs formation after stimulation with high dose of ADP. Patients with T2DM had higher platelet micro particles in all states with the ADP stimulation. (P = 0.004, SD: ±74.52). Conclusions: The flow cytometry data indicated that platelets were pre-active and associated with metabolic conditions in patients with type 2 diabetes mellitus. The induction of desensitization state helped platelets to reduce the platelet activation and sensitivity to ADP in a diabetic environment. Furthermore, the production of platelets micro-particles was high in the patients; and desensitized platelets were more susceptible to shedding of micro-particles. [ABSTRACT FROM AUTHOR]