Thrombocytopenia occurs frequently in patients with hematologic disorders and other diseases in hospital. Thrombocytopenia may cause bleeding, from mild to severe, which is treated for the patients. The cauese of death in thrombocytopenia cases in hospital is mainly (80%) due to uncontrolled bleeding and lack of platelet concentrates availability. The chemical on drugs that effectively to resolve thrombocytopenia through increase the thrombopoiesis mechanism still questioned. The purpose of this study was to explain the mechanism of the effect of fruit ethanol extract of Phoenix dactylifera L on thrombopoiesis increase in thrombocytopenia. The sample used 30 male rats were divided into 3 groups: negative control (K1): rats were given daily with CMC Na 0,5%; positive control (K2): rats were given heparin and CMC Na 0,5%; and the treatment group (K3): rats were given heparin and fruit ethanol extract of Phoenix dactylifera L dose of 10 mg /200 g BW. Furthermore, the cardiac blood sampling to calculate the amount of blood platelet and examination to bone marrow for expression of Hsp10, IL-6, cMpl, JAK2 with immunohistochemical methods. Result of this study showed that K3 (treatment group fruit ethanol extract of Phoenix dactylifera L) had significantly higher platelet counts (1125.50 ± 233.98) than control groups K1 (795.90 ± 224.75) and K2 (409.70 ± 79.67). There were increased expression of Hsp10 in stromal cells, IL6 in macrophages, cMpl and JAK2 in the cells of megakaryocytes. From the results of this study concluded that fruit ethanol extract of Phoenix dactylifera L is a potential treatment for increase thrombopoiesis on heparin induced thrombocytopenia in rats
