Effects of endotoxemia on thrombopoiesis in men

Background. Febrile conditions are often associated with increased platelet turnover acid refractoriness to platelet transfusions, although several py rogenic cytokines enhance thrombopoiesis. This study aimed to characterize the effects of experimental human endotoxemia on platelet turnover and thro mbopoiesis. Methods. Endotoxin (4 ng/kg) was infused into 30 healthy men to study the regulation of thrombopoiesis in systemic human inflammation. Pla telet counts, plasma thrombopoietin (TPO) and glycocalicin levels, and reti culated platelets (RP) were measured to evaluate the effect of acute endoto xemia on thrombopoiesis. Ten subjects received pretreatment with 1000 mg as pirin po, to evaluate possible effects of aspirin on platelet turnover, and ten subjects received paracetamol to control for effects of antipyresis. R esults, Platelet counts dropped by about 15% (p <0.001) one hour after LPS infusion, began to recover at 24 h, and exceeded baseline: values by 8% (CI : 5-12; p <0.001) at 7 days after LPS iv. Reticulated platelet counts incre ased from 1.62% (CI: 1.24-2.0) to a maximum of 2.39% (CI: 1.81-2.98; p = 0. 003) at 6 h. TPO levels increased from baseline values of 10 A.U/ml (CI: 8. 8-11.2) to 15.5 A.U/ml (CI: 13.6-17.3) at 24 h (p <0.001), whereas plasma g lycocalicin was not changed (p >0.05). The number of circulating platelet-n eutrophil aggregates increased more than 100% at 6 h (p <0.001). Neither as pirin nor paracetamol affected changes in any of the parameters measured. C onclusion. Low grade endotoxemia induces a rapid fall of platelet counts, w hich is followed by an early increase in reticulated platelets and TPO leve ls but not of glycocalicin levels. Finally peripheral platelet counts incre ase several days after LPS infusion.