L. Pirola

A methodology for biokinetic studies using stable isotopes: Results of repeated molybdenum investigations on a healthy volunteer

A method for biokinetic studies in humans using stable isotopes is presented. The technique is based on double tracer administration and on proton activation as the analytical method. As an application, the results of investigations on molybdenum metabolism in humans are reported. The contents of 95Mo and 96Mo in biological samples were determined by inducing (p,n) reactions and by analysing the gamma-rays emitted by the radioactive products. The minimum detectable quantity was 2 ng/mL plasma for both Mo isotopes. Four investigations on molybdenum metabolism were performed on a healthy volunteer subject in the course of 3 yr. Two absorption studies with different amounts of tracers in aqueous solution were performed by giving 96Mo orally and 95Mo intravenously. Two investigations were performed with single oral administration of 96Mo in aqueous solution and of a 96Mo solution mixed with an infant formula respectively. The stability with time of the biokinetic parameters was tested. The fractional absorption values measured in this volunteer were 0.84, 0.98 and 0.95 for three studies with Mo in HCl and 0.51 for a single study with Mo administered in an infant formula, these data are discussed.

Proton nuclear activation in stable tracer technique for ruthenium metabolism studies

Abstract 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 99 Ru and 101 Ru 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 tracer technique, one male rabbit was orally given 1 mg of 99 Ru and was injected 78 μg of 101 Ru. 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.

Cadmium and titanium in human serum determined by proton nuclear activation

An investigation of the quantitative content of Cd and Ti in human serum samples by proton nuclear activation (PNA) has been performed and the results are presented. The activation has been induced by a 13.5 MeV proton beam of the AVF cyclotron of the University of Milan, via a (p, n) reaction on the nuclei of the target. For the quantitative determination a known amount of a reference element has been added to the samples and comparison has been made with a standard sample containing also known quantities of the elements studied. Response linearity, reproducibility and possible contaminations have been tested.

An iron metabolism study in humans by means of stable tracers

An investigation of iron metabolism in a female patient volunteer by administration of stable iron isotopes as tracers was performed. The applied methodology had already been tested in rabbits in comparison with radioactive tracer technique. The subject under study was given 58Fe solution intravenously and about 45 min later 57Fe solution orally. Ten blood samples were drawn at different times within 522 min from injection. Single iron isotopes content in plasma samples was determined by proton nuclear activation. A Compton suppressor system was utilized to improve the detector limits. The characteristic parameters of iron plasma clearance and of iron intestinal absorption were determined.

Molybdenum metabolism studied by means of stable tracers.

An investigation on molybdenum metabolism by administration of molybdenum stable isotopes was performed. Fractional intestinal absorption was determined in animals by the double tracer technique. The investigated subjects were given an enriched solution of Mo-96 orally and, a few minutes later, an enriched solution of Mo-95 intravenously. Blood samples were drawn at different times following the tracer administration. The Mo-95 and Mo-96 contents in plasma samples were determined by proton nuclear activation. The described methodology offers a means for the study of molybdenum metabolism in humans without radiation risk.

Intestinal absorption of tellurium studied with stable tracers

An investigation on tellurium metabolism by administration of stable tellurium isotopes124Te and126Te has been performed. Fractional intestinal absorption was determined in rabbits by the double tracer technique. The investigated subjects were given an enriched solution of one tellurium isotope orally and a few minutes later an enriched solution of the other isotope intravenously. The124Te and126Te contents in plasma samples were determined by proton nuclear activation. The methodology described offers a means to study tellurium metabolism in humans without radiation risk.

Ferrokinetic studies with stable isotopes as tracers

A methodology for ferrokinetic studies based on the administration of iron stable isotopes was developed. Fractional plasma clearance and intestinal iron absorption in rabbits were determined using the double tracer technique. Three rabbits were given 58Fe solution intravenously and about 40 min later 57Fe solution orally. Blood samples were drawn at different times following administration. The analysis of the single iron isotopes content in plasma samples was made by proton nuclear activation. The results were compared with those obtained from the administration, to the same rabbits, of the radioactive isotopes 55Fe and 59Fe. The agreement was found to be satisfactory.

Response to a single oral test of molybdenum stable isotopes for absorption studies in humans

Two volunteer subjects were given orally enriched solutions of Mo-95 and Mo-96 respectively. Blood samples were drawn at various times following the tracer administration. The Mo-95 and Mo-96 content in plasma samples was determined by proton nuclear activation and the response to the single oral test of enriched stable molybdenum isotopes was determined. Assuming a simple two-open-compartment model where the first compartment is the gastrointestinal tract and the other is the plasma, an indicative value of the fractional intestinal absorption for the two subjects is given. The feasibility of direct quantitative measurements of Mo intestinal absorption by the double-tracer technique, using stable tracers, is evidenced.

CHROMIUM IN HUMAN SERUM DETERMINED BY PROTON ACTIVATION

A method for Cr determination in biological samples based on proton nuclear activation is presented. The activation was induced by a 13.8 MeV proton beam of the AVF Cyclotron of Milan University via a (p, n) reaction on the nuclei of the target. For the quantitative determination Cd has been chosen as reference element. The method has been applied to Cr determination in human serum samples. The experimental procedure is described and results are presented and discussed.

Irradiation chamber for the simultaneous nuclear activation of several targets

Abstract In this work an irradiation chamber, used for simultaneous proton activation of several samples in the same experimental conditions, is described, together with its refrigerating system. After a brief technical representation, a rough approach to the thermal behaviour of the whole system is made, in order to evaluate the maximum temperatures reached by the device and by the samples. Experimental measures are in good agreement with calculated values.