ACTIVITY IN THE GASTROINTESTINAL-TRACT AFTER ADMINISTRATION OF BONE-SEEKING RADIOPHARMACEUTICALS - EXPERIMENTAL STUDIES IN MICE

Purpose: To test the possibility that (radio)activity of non-pertechne tate nature is excreted into the gastrointestinal tract at bone scinti graphy. Material and Methods: The distribution of a bone-seeking radio pharmaceutical (Tc-99m-HDP) was studied in an experimental mouse syste m by dissecting different organs and assessing their activity with a g amma-counter. Results: A comparison of the activity of the submandibul ar glands, which are assumed to accumulate only pertechnetate, and the gastrointestinal tract showed that a significant fraction of the acti vity excreted into the gastrointestinal tract did not consist of perte chnetate. Part of the excretion took place in the stomach. It was not connected to a specific bone-seeking agent or Mo-99/Tc-49m generator, Nor did it increase with time between make-up and injection. The excre tion of the non-pertechnetate acitvity was reduced by cimetidine and o meprazole. These gastric-secretion blocking drugs did not reduce excre tion of pertechnetate or significantly affect the general distribution of the radiopharmaceutical. Conclusion: There is a significant excret ion of non-pertechnetate activity in the gastrointestinal tract. Part of this may be caused by excretion of the undegraded radiopharmaceutic al by the stomach mucosa.