PROTON NUCLEAR ACTIVATION IN STABLE TRACER TECHNIQUE FOR RUTHENIUM METABOLISM STUDIES

A methodology is presented, based on proton nuclear activation (PNA), for the contemporary determination of two stable isotopes of ruthenium in biological samples. This technique can be successfully applied in studying the biokinetics of oligoelements, avoiding radiation hazards. On the basis of the possible proton-induced nuclear reactions and the decay characteristics of radioactive products, (p, n) reactions on Ru -99 and Ru-101 resulted to be the most convenient. The minimum detecta ble quantities resulted to be 15 and 3 ng/ml of plasma respectively. R u fractional intestinal absorption in an experimental animal was deter mined, as a feasibility test for applications to humans. Following dou ble tracer technique, one male rabbit was orally given 1 mg of Ru-99 a nd was injected 78 mu g of Ru-101. Eleven blood samples were drawn wit hin 300 min after administration. Concentrations in plasma samples of intravenously and orally given Ru tracers are reported, as a function of time after administration. Fractional intestinal absorption was det ermined from concentrations of both isotopes, using the convolution in tegral technique. A Ru intestinal absorption of (5.5 +/- 0.8)% within 300 min from the oral administration was obtained. The results show th e effectiveness of this methodology and its applicability for future i nvestigations in humans.