Kinetics of acute inflammation by E coli in rabbits. Quantitation of blood flow, enhanced vascular permeability, hemorrhage, and leukocyte accumulation

The inflammatory response to Escherichia coli was quantitated in the skin of rabbits. The lesions were studied up to 24 hours. The vascular permeability increase, measured with ¹²⁵I-albumin, reached a peak 2 hours after injection of bacteria and subsided after 4 hours. Hyperemia measured with ⁵⁷Co- or ¹¹³Sn-labeled microspheres, reached its maximum value around 3 hours, and diminished after 5 hours. In the 24-hour-old lesions both vascular permeability and hyperemia remained at values twice as high as those of control skin sites. The rate of leukocyte accumulation was measured using ⁵¹Cr-labeled autologous leukocytes. It reached peak values by 2 hours. Microscopic examination showed that the number of neutrophils remained almost unchanged between 4 and 24 hours after the injection of bacteria. ⁵⁹Fe-labeled erythrocytes were used to quantitate hemorrhage. Hemorrhage was measurable by 2 hours and plateaued after 4 or 6 hours. It remained at the plateau levels for the 24 hours of the experiment.