Organ distributions and clearance studies of 99mtechnetium-labeled Corynebacterium parvum in patients with leukemia

The clearance, metabolism and localization of Corynebacterium parvum (C. parvum) labeled with 99mtechnetium (99mTc) given intravenously was studied in various leukemia patients to develop the method and to evaluate reticuloendothelial systems (RES) function. A computer program was utilized to characterize the clearance. C. parvum 0.05 mg was labeled aseptically with 10 mCi of 99mTc with a reducing agent. It was injected intravenously over 5 s and clearance was characterized over the next 60 min. The low dose of C. parvum did not cause any symptoms. The blood or plasma clearance time (t 1/2) was in the range of 0.65 to 1.96 min, in eight patients. By whole body imaging, the distribution of C. parvum was found mainly in the liver, and to a much lesser extent in the spleen, lungs, and bone marrow. Nonparticulate 99mTc (which was not sedimented by centrifugation of blood samples at 3000 rpm for 30 min) appeared rapidly in the blood after i.v. injection accounting for more than half of the radioactivity in a few minutes. In vitro incubation of 99mTc labeled C. parvum with saline, whole blood, serum or leukocytes revealed that the release of free 99mTc resulted from the combined action of serum and leukocytes. The rapid clearance will limit the utility of this preparation in characterizing RES function in man and its modification by disease or therapy.