## 4 Discussion
### Reproduction Parameters  
In the Cd group, the number of litters, the number of born pups and the number of raised pups for the entire period of the experiment were lower than in the K group. Lower numbers of born pups per litter and raised pups per litter compared to the K group were recorded. Cd acts preferentially through deprivation of testosterone secretion [16], as well as through the hypothalamus--pituitary--testes axis [11]. [PERSON] et al. [27] indicated that, even a very small difference in the administered dose of Cd in males causes a sudden increase in testicular damage. [PERSON] [32] stated that cadmium can affect the female reproductive and endocrine systems and hormone levels change. It is assumed that lower values of some monitored reproductive parameters in the Cd group compared to the K group indicate a decrease in reproductive function in rats. In general, the number of born pups per litter and the number of raised pups per litter are among the most important indicators of reprotoxicity. A similar conclusion was achieved at a concentration of 20 mmol\(\cdot\)L\({}^{-1}\), i.e., 2.0 mg Cd per litter [16]. The body's response to low doses may vary [3]. One example of the unexpected hormonal effect of a toxic substance is the finding that cadmium acted as a hormonally active substance even in concentrations that were considered safe. In a multigenerational study in rats at doses up to 100 mg Cd per kg of live weight no adverse effects on reproduction have been reported. In a four-generation study at a dose of 1 mg\(\cdot\)L\({}^{-1}\) in water and at a mean daily dose of 0.125 mg Cd\(\cdot\)kg\({}^{-1}\cdot\)day\({}^{-1}\), no adverse effects on fertility were observed in rats and mice. However, at a dose of 50 mg Cd\(\cdot\)kg\({}^{-1}\) of live weight, slight testicular changes were observed in rats during a 15-month period [33]. In terms of the effect of cadmium on animals in chronic poisoning, the highest accumulation of cadmium occurred in rabbits(females) in the ovaries (0.47 mg\(\cdot\)kg\({}^{-1}\)), uterus (0.25 mg\(\cdot\)kg\({}^{-1}\)) and testes (0.10 mg\(\cdot\)kg\({}^{-1}\)) [34]. [PERSON] and [PERSON] [35] described the embryotoxic effects of cadmium in rodents, i.e., fetal malformations (cleavage of the climate, oligodactylia, polydactylia, exencephalic and others). In the Hg group, the numbers of litters born pups and raised pups for the entire period of the experiment were lower compared to the K group. The number of born pups per litter and the number of raised pups per litter in the Hg group were higher but insignificantly compared to the K group, which could be attributed to the adaptation process to a certain environment with a certain load factor. However, it is very similar to hormesis after exposure to a low dose of harmful substances. At low doses of mercury, there may be no signs of a toxic effect on the body. However, it can cause increased production of proteins from the group of matalothionines, which bind heavy metals and ensure their subsequent removal from the body. In addition, the role of metallothioneein is to protect cells from further damage (e.g., from heritable information damage). Therefore, it is possible that the low dose of mercury was not only not dangerous for the organism, but also contributed to the organism becoming more resistant to the adverse effects to which it was exposed. A similar finding was made by [PERSON] et al. [36] but at a concentration 200 times higher than the MPC in water containing HgCl\({}_{2}\) at a concentration of 1 mmol\(\cdot\)L\({}^{-1}\) (0.2 mg Hg\(\cdot\)L\({}^{-1}\)). If the results in this study are attributed to the hormetic effect, there can be a logical explanation. The low doses of the toxic substance used in the cells did not have to cause much damage; on the contrary, they were able to trigger protective reactions in the cell which prevented the action of other adverse effects. However, this assumption, based on the results of this study, requires further experimental studies.