USE OF COLLOIDAL GOLD AND NEUTRON-ACTIVATION IN CORRELATIVE MICROSCOPIC LABELING AND LABEL QUANTITATION

Albumin was conjugated to 16 nn gold particles (Alb-Au-16) and infused into anesthetized pigs to determine if plasma, tissue and bronchoalve olar lavage (BAL) fluid concentrations of gold could be quantitated by neutron activation (Au-198). Additionally, transmission electron micr oscopy (TEM) of lung and liver samples was evaluated for sites of gold distribution and morphological changes. The minimum concentration of gold detected by neutron activation ranged between 1.4 and 1.9 ppb (ng /gm of sample). No gold was detected in the plasma of pigs prior to Al b-Au-16 infusion, while mean post infusion concentrations were 1.037 /- 0.69 ppm (mu g/gm plasma, +/-SD). The concentrations in the lung an d liver were 274.4 +/- 0.03 and 88.3 +/- 0.04 ppm, respectively. There was no measurable Alb-Au-16 in the BAL fluid. TEM showed gold particl es within phagolysosomes in pulmonary and hepatic intravascular macrop hages. No morphological changes were observed within the two populatio ns of macrophages and no gold particles were observed within the alveo lar space. Neutron activation of blood, tissue and BAL fluid samples f rom pigs administered intravenous Alb-Au-16 was sensitive to the ppb c oncentration. The capability of neutron activation to detect very low concentrations of Au-198 combined with the freedom from contamination, make neutron activation an excellent technique for the study of the d istribution and metabolism of a substance in vivo.