Time-concentration curves and dilution spaces of T-1824 and I131-labeled proteins in dogs

Five-hour time-concentration curves were obtained after injection of T-1824, I131-labeled human albumin, and I131-labeled dog fibrinogen. The albumin and fibrinogen curves can be roughly divided into 3 segments (0–20 min, 20–70 min, and 70–310 min), each showing a different mean slope. The T-1824 curves show only one change in slope, at 20 min. After at least 70 min the dye left the circulation at a much greater rate than either of the iodinated proteins. Thoracic duct lymph return indicated that 12.9% of the injected iodinated albumin, 8.3% of the T-1824, and 6.3% of the iodinated fibrinogen was returned over the 310-min period. The spaces measured by the T-1824 and the iodinated albumin were not significantly different, whereas the fibrinogen measured a significantly smaller space than either of the former. It is inferred that the dye-protein complex might be broken within the vascular system. Also, the loss of fibrinogen from the capillary is less han for the iodinated albumin.