Reduced clearance of leukocytes from lungs in septic rats

Leukocytes have previously been shown to sequestrate in the lungs and liver in association with traumatic and septic shock. In a rat model of gram-negative sepsis of intra-abdominal origin, a previously described in vivo technique was used for dynamic studies of leukocyte sequestration in different organs using white blood cells labeled with 111-indium-oxine. One group of rats was either studied immediately after induction of sepsis or for 6 h under a scintillation camera for continuous registration of the activity distribution (i.e., presence of leukocytes). Another group was studied 12 h after induction of sepsis for 60 min. The activity increased immediately over the lungs, indicating sequestration of the leukocytes during the first 6 h, but there was no significant difference in this respect between septic and control animals. It does not seem possible to study leukocyte sequestration dynamically in this way. When the labeled leukocytes were administered 12 h after induction of sepsis, however, the activity of septic animals' lungs was seen to remain elevated over the time period studied compared with control rats, in which the activity slowly decreased. In the liver and spleen, the activity increased in both groups, but significantly more so in control animals, which may be explained by disturbed leukocyte margination and cell turnover in the septic animals. This study has indicated that leukocyte distribution in different organs is affected by sepsis and this reaction can be studied using radiolabeled leukocytes.