Megakaryocytic emperipolesis in the rat bone marrow induced by lipopolysaccharide.

Megakaryocytic emperipolesis was observed in the rat bone marrow when lipopolysaccharide (LPS) was administrated intravenously at a daily dose of 0.5 mg/kg body weight for 4 weeks. Emperipolesis was significantly increased in the LPS-treated group (3.54%) as compared with the control group (1.35%). Histologically, several types of hematocytes were engulfed within megakaryocytes, but the host cells and entering hematocytes showed no degenerative alterations. Morphologically, most megakaryocytes showing emperipolesis were classified into the mature type indicating high platelet producting ability but platelet counts in the peripheral blood were markedly reduced in the LPS-treated group (63.7 x 10(4)/mm3) as compared with the control group (128.4 x 10(4)/mm3). These results suggest that the emperipolesis is a phenomenon closely related to the marked reduction in the number of platelets and accelerated platelet production of megakaryocytes.