PROTON ACTIVATION-ANALYSIS OF STABLE ISOTOPES FOR A MOLYBDENUM BIOKINETICS STUDY IN HUMANS

Molybdenum is a trace element essential to life. Nevertheless, Little information is available on its metabolism in humans. A methodology ba sed on stable isotope administration that combines compartmental analy sis, simultaneous use of two tracers, and proton nuclear activation (P NA) is presented. A four-compartment metabolic model was adopted. The compartments are stomach, small intestine, transfer compartment, and u nquantified tissue pool. The employment of two different stable isotop es of the element under investigation as tracers was made possible by PNA. Optimization of the technique for molybdenum determination in pla sma led to the choice of Mo-95 and Mo-96 as tracers. Their concentrati ons in plasma can be determined measuring the disintegration gamma lin es of the corresponding technetium radioisotopes produced via (p,n) re action. In the adopted experimental conditions, a minimum detectable c oncentration of 2 ng isotope/ml plasma was attained. A kinetics study was performed on two healthy volunteers. To both subjects one tracer w as orally administered, and the other intravenously injected. Venous b lood samples were withdrawn at different postinjection times and the c oncentrations for both isotopes determined. The model parameters descr ibing molybdenum kinetics were obtained for the two individuals. Total absorbed fraction was found to be 0.84+/-0.03 and 0.86+/-0.07, respec tively.