Late Effects of Subchronic Cadmium Exposure on Metallothionein Gene Expression in Rat Kidneys

Heavy metals, due to their ability to bioaccumulate and are highly toxic even in low concentrations, are the most dangerous environmental pollutants, especially in industrialized countries. The purpose of the study was to evaluate the degree of cadmium accumulation, as well as the expression of the Mt1a and Mt2a genes, in the kidneys of rats using two experimental models of subchronic intoxication with cadmium chloride. A total of 80 adult white outbred rats of both sexes were equally distributed into four groups: a control group (negative control), group 1 (0.001 mg/kg/day CdCl₂), group 2 (0.01 mg/kg/day CdCl₂), 3rd group (0.1 mg/kg/day CdCl₂). After three months of exposure, 10 animals (5 males and 5 females) were randomly selected from each group and euthanized, followed by kidney samples for cadmium analysis and gene expression assessment. The remaining animals (n = 40) were left for an additional 30 days without treatment, before being sacrificed to collect tissue. The results showed that 1 month after cadmium withdrawal, the processes of redistribution of the metal in the body are still ongoing, which is expressed in a greater accumulation of cadmium in the kidneys. We also recorded an increase in the Mt1a gene expression and a decrease in the Mt2a gene expression in the kidneys of animals that went through the remission stage compared to animals without it. These data suggest that even after Cd withdrawal, there may be long-term negative effects on the kidneys.