Iodinated E. coli 70S ribosomes as a radiocolloid of uniform particle size for lymph-node and liver scanning

As an example of the use of biologic particles as carriers for radioactive tracers, E. coli 70S ribosomes were labeled with I-125 using chloramine-T. The labeled ribosomes, after treatment with glutaraldehyde, were injected into rabbits either subcutaneously (through the dorsum of the foot) or intravenously (through the ear). After subcutaneous injection, 40% of the activity accumulated in the lymph nodes during the first 5 hr, and the 70S ribosomal particles were shown to remain within the lymphatic system for at least 8 hr. After intravenous injection, 71% of the activity was detected in the liver within minutes by scintigraphic techniques. The effective half-time of the label in the liver from glutaraldehyde-treated I-125-tagged 70S ribosomal colloidal particles is 4-5 hr. No pyrogenic response was observed. Barring any deleterious side effects, the results indicate that biologic cell components of definite dimensions (in this case E. coli 70S ribosomes about 20 nm in diam) could be considered as radiocolloids for lymph-node and liver imaging.