[Kinetic observation and analysis of the radioactivity distribution of 125I-labelled F(ab')2 fragments of monoclonal antibody against human lung cancer cells in normal mice].

ABSTRACT

Radioactivity distribution of 125I-labelled F(ab')2 fragments in 14 organs and tissues of normal mice for 11 time-phases from 0.5 hour to 7 days after injection was observed. The radioactivity-time curves of these organs and tissues were divided into three types according to their characteristics excreting type (blood and liver), absorbing type (thyroid), absorbing-excreting type (the other organs and tissues). The organs fully perfused with blood had shorter peak-time and higher peak-value, such as heart, lung, kidney and liver. All of the peak-times were equal to or less than 2 days after injection, therefore the image taking should be kept away from this period. The excreting rate constants of slow metabolic component were similar for various organs and tissues except thyroid and brain. The brain had a low peak in the curve and small excreting rate constant. It was demonstrated that F(ab')2 fragments were able to penetrate the blood-brain barrier but absorption and excretion were slower compared with the other organs and tissues. The radioiodine was obviously concentrated in the subcutaneous tissue, which may have been the main cause of the subcutaneous tissue tumor induced by radioiodine. The radioactivity-time curve in which the peak value and inflect point existed simultaneously shows that radioactivity metabolism after injection of 125I-F(ab')2 follows three compartment models. The biological meanings corresponding to three sections of the blood radioactivity-time curve are pure distribution, distribution-recycle and catabolic-excretory phases, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)