Properties of the cadmium and selenium complex formed in rat plasma in vivo and in vitro

Following the simultaneous subcutaneous administration of CdCl2 and Na2SeO3 to rats, evidence of a Cd-Se complex was detected in plasma by gel filtration chromatography. A similar complex was found in plasma after incubation of selenite, Cd, rat erythrocytes, and plasma in vitro, and after incubation of H2Se, Cd, and plasma in vitro. No interaction of selenite, selanete, or selenodiglutathione with Cd and plasma in the absence of erythrocytes in vitro was noted. Characterization by gel filtration, ion-exchange chromatography, affinity chromatography, and ammonium sulfate fractionation showed that these Cd-Se complexes are similar. The results support the hypothesis that H2Se or a similarly reduced selenide is the product of selenite metabolism by rat erythrocytes. Hydrogen selenide also altered the distribution of inorganic mercury in rat plasma in vitro in such a way that the apparent molecular weights of the Se-Hg and Cd-Se complexes associated with protein were similar. Hydrogen selenide had no effect upon the distribution of methylmercury in plasma. The stability of the Cd-Se complex in plasma depended upon the integrity of the native protein components, as shown by incubation with Proteinase K. The properties of the complex suggested that it existed in a single form associated with different plasma components under various conditions.