Late Effects of Endotoxin on the Accumulation and Function of Monocytes in Rabbit Lungs

Recent studies from our laboratory show that the lung contains a marginated pool of monocytes. The present study was designed to investigate monocyte accumulation in this pool 4 to 28 h after a single dose of endotoxin when the endotoxin had disappeared from the circulation. This was accomplished by administering a single intravenous dose of endotoxin (Escherichia coli, 50 µg/rabbit) to unanesthetized animals (n = 6) and saline to controls (n = 5) at time 0. Four hours after this dose of endotoxin, 111In-monocytes (93.5% pure) isolated from donors were injected intravenously, and, at 27 h, the rabbits were anesthetized and colloidal carbon (CC, 1 ml/kg body weight) was injected intraarterially to provide a phagocytic stimulus. The animals were sacrificed at 28 h, and the lungs were fixed in situ with glutaraldehyde. The data show that lungs from the endotoxin-treated rabbits contained 4.8 times more 111In-monocytes than controls, that 92% of these radiolabeled monocytes were in the alveolar capillaries, a...