Experimental sepsis: characteristics of activated macrophages and apoptotic cells in the rat spleen.

Sepsis, being characterized by massive translocation of bacteria into tissues, induces the suppression of the function of both leukocytes and macrophages. The aim of the study was to count activated macrophages (AMs) and apoptotic (Ao) cells in the rat spleen during the period of experimental sepsis and to clarify the associations of these parameters with each other and with leukocyte migration and bacterial translocation into different organs. The Wistar rats were intraperitoneally inoculated with Escherichia coli (E. coli) and were sacrificed after 2, 6, 24, 48, and 120 h. Bacteria and leukocytes in tissues were specifically stained. AMs were identified by immunohistological staining and Ao cells by the TUNEL assay. The high counts of E. coli at 6 h were strongly associated with a low level of the total counts of leukocytes, accompanied by the high translocation of microbes into tissues. In the spleen, lymphocytes, macrophages, and neutrophils with pyknotic nuclei were identified. The count of AMs was highest at 24 h after the inoculation with E. coli; at the same time the Ao cell count began to rise and achieved the highest level 24 h later. Our investigation indicates that the molecular peculiarities of macrophages and their responses to the inflammation process are tissue-specific. In the spleen the activation process involving hematopoietic cells and macrophages was remarkable at the late stage of sepsis, characterized by a high count of Ao cells.

Changes of activated macrophages and apoptotic cell count in the organs of rats during experimental sepsis.

OBJECTIVE: Leukocyte migration plays an important role in inflammation. The aim of our study was to detect the activated macrophage count and to define the apoptotic cell count in the rat's liver and lungs during different stages of sepsis and to clarify whether the activity of macrophages is associated with the apoptotic cell count in the course of the septic process. MATERIAL AND METHODS: Experimental sepsis was induced by inoculating Wistar rats intraperitoneally with E. coli cells. The liver and lung tissue was obtained 2, 6, 24, 48 and 120 hours after inoculation, and blood smears to detect the leukocyte volume were prepared at the same time. Macrophage activity was studied by immunohistochemical staining, using the ABC method. Apoptotic cell count was detected with the "In Situ Cell Death Detection Kit". RESULTS: Decrease in the total count of leukocyte and lymphocyte percentage and a rise in the percentage of neutrophils in the blood were evidences of a strong inflammation process in an organism. The count of activated macrophages in the liver was high, showing the maximum level at the end of the 2(nd) h after inoculation, after which it began to fall. Apoptotic cell count rose after a decrease in macrophage activity. In the lungs both changes - a decrease in activated macrophage level and a rise in the apoptotic cell count took place later on. CONCLUSION: Our investigations indicate that a decrease in the activated macrophage level is connected with an increased rise in the apoptotic cell count in both organs depending on the stage of the disease and occurs in the liver earlier than in the lungs but the process of cell apoptosis was more intensive in the lungs.