Effect of arsenic trioxide on metallothionein and its conversion to different arsenic metabolites in hen liver

The metabolism of arsenic, its affinity to metallothionein (MT), its influe nce on selenium levels, and its biotransformation to different metabolites in the liver tissue of laying hens exposed to arsenic trioxide (As2O3) was investigated. The experiment was performed with two groups of hens fed for 19 d with either a standard diet or with the same diet enriched in arsenic (30 mug/g). The major findings were as follows: 1. After 19 d exposure, about 65% of the total liver As was found in the wa ter-soluble phase (100,000g centrifuged supernatant). In liver supernatant, As binding was found mostly in the range of very low-molecular-weight prot eins (M-r < 10,000). Although after exposure the amount of MT-like proteins increased, the As bound to it was only in trace amounts. The protein was i dentified by convential procedures as Zn,Cu-thionein with traces of seleniu m and arsenic. 2. Arsenic exposure resulted in almost unchanged Se levels regarding its ti ssue concentrations and distribution between supernatant and pellet, where about 10% of total Se was found in the supernatant. On the contrary, As exp osure did affect Cd levels. Tissue Cd concentration was slightly diminished , but the percentage of tissue Cd found in the water-soluble phase was incr eased from 20% to 40%. 3. In methanol extracts of tissue and supernatant of the As-exposed group, only two arsenic compounds were detected, As(III) and dimethylarsinic acid (DMA), the latter prevailing.