Use of mini-microaggregated albumin to study reticuloendothelial system (RES) function in C. parvum-treated animals.

Mini-microaggregated albumin colloid (particle size less than 80 A) and microaggregated albumin colloid (particle size 500-1000 A) made from human serum albumin were conjugated with 99mtechnetium and used to study reticuloendothelial system (RES) function in animals treated intravenously with C. parvum. The uptake in blood, liver and spleen were studied in untreated mice and in mice at various times after treatment with 150 or 300 micrograms of C. parvum. The blood clearance of these materials was studied in rabbits before and at various times after treatment with 0.5 mg/kg of C. parvum. In mice, 80 A-microaggregated albumin was cleared significantly faster from the blood and localized to a greater extent in the liver and spleen after C. parvum treatment. There was a positive correlation between the increased organ weight induced by C. parvum and the accelerated clearance of 80 A-microaggregated albumin. The 80 A-microaggregated albumin was also cleared more rapidly from the blood of rabbits after C. parvum treatment. These studies suggest that 80 A-microaggregated albumin labeled with 99mTc is a useful tool for study of RES function in animals and because of its relatively long t 1/2 may also be useful for studies of human RES function.