Lead, chromium and thallium metabolism investigated by nuclear and radiochemical techniques

Abstract The investigation of the metabolism of environmental doses of trace metals at cellular levels in mammals is a matter of great difficulty and not only because of determining the amount of trace metals present in whole organs. Problems of detection and measurement of the metals incorporated into intracellular fractions or associated to biomolecules are serious due to the concentrations to be determined, part-per-billion or less. Radiotracers and nuclear techniques largely overcame the considerable technical problems associated with toxicological experiments on trace metals. In particular, when radiotracers are used to label trace metal compounds for metabolic purposes, requirements for high specific radioactivity are stringing if the work is to be carried out at current environmental trace metal levels. In addition, purely instrumental neutron activation analysis (NAA) is in many cases not sufficient in determining trace metal levels as present in tissues, body fluids and cellular components. Radiochemical neutron activation analysis (RNAA) is some time necessary in order to approach the theoretical detection limits of NAA. This work summarizes in vivo and in vitro studies on the metabolic patterns of Pb, Cr and Tl by radiochemical neutron activation analysis (RNAA) and 203 Pb, 201(204) Tl, 51 Cr radiotracers prepared at the cyclotron or nuclear reactor. In particular, applications are referred: (i) to the distribution of the three elements in rat tissues, subcellular fractions and molecular components; (ii) to investigations concerning interactions and biochemical mechanisms on isolated biological systems. The use of NAA for the determination of Cr in tissues of humans affected by some diseases is also briefly presented.