Proton nuclear activation in stable tracer technique for ruthenium metabolism studies

A methodology is presented, based on protonnuclearactivation (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 99Ru and 101Ru resulted to be the most convenient. The minimum detectable quantities resulted to be 15 and 3 ng/ml of plasma respectively. Ru fractional intestinal absorption in an experimental animal was determined, as a feasibility test for applications to humans. Following double tracertechnique, one male rabbit was orally given 1 mg of 99Ru and was injected 78 μg of 101Ru. Eleven blood samples were drawn within 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 determined from concentrations of both isotopes, using the convolution integral technique. A Ru intestinal absorption of (5.5 ± 0.8)% within 300 min from the oral administration was obtained. The results show the effectiveness of this methodology and its applicability for future investigations in humans.