Abstract
Carrier-free [65]Zn and [67]Ga produced in the M.R.C. cyclotron were used to study the metabolism of zinc and gallium in rats. The appropriate literature has been reviewed. Zinc excretion has been studied using a sub-physiological tracer dose of [65]Zn. In 25 days 80% of the dose was excreted in the faeces. The secretions of the pancreas and liver contributed approx. 30% of the faecal [65]Zn, and it is suggested that the origin of approx. 70% of faecal zinc is the secretions of the Paneth cells and goblet cells and other gastro-intestinal secretions. Evidence is presented that the zinc secreted in bile is in the form of a macromolecular complex. The distribution and turnover of zinc in a number of soft tissues have been studied. The effect of oral ZnSO[4] on the tissue retention of endogenous [65]Zn has been studied. The significance of these results and their relevance to the use of radionuclides of zinc as pancreas and prostate gland scanning agents have been discussed. Tissue distribution and excretion of [67]Ga and its localisation in transplanted tumours have been studied. Gallium was retained in the body due to plasma protein binding and tissue deposition, resulting in its slow excretion. [67]Ga localised mainly in viable tumour cells.