Cadmium distribution and metallothionein expression in rat organs following acute intoxication

Introduction. This article presents the results of experimental simulation of the acute toxic effect of cadmium on the rat organism, its distribution in the liver, and kidneys. Activation of the protective mechanism against toxic metal through the metallothionein protein has to reduce the bioavailability of free cadmium.

Material and methods. The study was conducted on rats weighing 140-190 g, which was once intragastrically injected with cadmium chloride in an amount of 1/20 LD50. We studied the time intervals: before intoxication, 1, 2, 4, 6, 24, 48, and 96 hours after inoculation. The accumulation of cadmium in the liver and kidneys was measured by atomic absorption spectrometry. The expression of the metallothionein gene (МТ1, МТ2А, МТ3) was determined using RT-PCR on RNA isolated from the same organs.

Results. Quantitative differences in the metal content in the liver and kidneys are observed 1 hour after intoxication, with a cadmium content of 250 and 125 times higher than in the control groups, respectively. There is an accumulation of cadmium in the liver with a maximum after 6 hours, and then its redistribution to the kidneys. The pronounced expression of metallothionein with a single acute exposure to cadmium is tissue-specific, so the expression of the MT1 and MT2A genes was greatest in the liver and the MT3 gene in the kidneys.

Discussion. After administration cadmium is mainly localized in hepatocytes and its concentration may exceed the ability of metallothionein to bind cadmium ions, which leads to histopathological changes in the liver. In response to the intake of metal in the cell, the expression pattern of many genes, including those associated with the activation of protective reactions, changes.

Conclusion. Our data show a single exposure to cadmium to lead to an increase in the content of MT transcript in the liver and kidneys, simultaneously with the accumulation of metal in them. The nature of this accumulation depends on the organ, on the time of exposure, and gene expression also on the form of MT.