DOI: https://doi.org/10.62204/2336-498X-2023-3-14

CHANGES IN THE MICROELEMENT

COMPOSITION OF THE HEART OF RATS UNDER

CHRONIC INTOXICATION WITH CADMIUM

Vira Shatorna,

Doctor of Biological Sciences, Professor
Dnipro State Medical University, Ukraine,
verashatornaya67@gmail.com;  ORCID: 0000-0002-5853-9864

Vira Harets,

Doctor of Biological Sciences, Professor
Dnipro State Medical University, Ukraine,
haretsvira@gmail.com; ORCID: 0000-0003-0141-1736

Larysa Lomyha,

Dnipro State Medical University, Ukraine,
lomygal@gmail.com; ORCID: 0000-0002-7881-1386

Annotation. Cadmium is a heavy metal that enters the body in various ways, is involved in metabolic processes, accumulates in tissues and organs and can cause pathological changes and diseases. Thus, cadmium significantly affects the condition of the liver and kidneys, nervous, cardiovascular and reproductive systems. Copper and zinc show the ability to compete with cadmium for certain receptors or metabolic pathways, which allows them to reduce its negative effects. This may open prospects for the use of copper and zinc as potential bioantagonists. This competitive process can lead to a decrease in the absorption of cadmium by cells, which, in turn, reduces its toxic effect. The interaction of cadmium with copper or zinc is a complex process, and indicators of the level of accumulation of these metals in the embryos and hearts of female rats, as well as indicators of the heart mass index, can somewhat clarify the toxicological and antagonistic nature of these interactions. Understanding these processes is important for the development of strategies to protect against cadmium toxicity and the further development of preventive measures in maintaining heart health. The study was conducted on pregnant female Wistar rats during the entire gestation period, which were divided into 4 groups. Indicators of quantitative accumulation of cadmium, copper and zinc in the embryos and hearts of females in all four groups were analyzed, which made it possible to reveal certain regularities of interactions between copper and zinc in relation to cadmium.

Keywords: heavy metals, cadmium, zinc, copper, heart, rat embryos.

Introduction. Heavy metal ions are biologically active and participate in many physiological and pathophysiological reactions. As a result of the body absorbing cadmium, it is easily transported [1], distributed and accumulated in tissues and organs, causing a negative effect on the body. Even in low doses, cadmium has a toxic effect on the nervous system, reproductive and cardiovascular systems [2, 3]. Because the cadmium is actively involved in physiological processes [4] and is able to overcome the placental barrier, its accumulation leads to a change in the activity of various enzymes, a shift in the main morphological indicators, and also significantly disrupts the balance of microelements in the adult body of the rat and embryos [5]. Cadmium is able to increase the content of certain trace elements, causing their retention in tissues and organs, and vice versa – to cause significant losses of certain divalent cations, replacing them with itself. The level of cadmium accumulation depends on the dose, duration of intoxication, method of administration, chemical formula of the compound, type of tissue or organ, age and physiological state of the organism.

The aim of the study. To determine the effect of zinc and copper succinates with their simultaneous chronic administration on the level of cadmium accumulation in the embryos and hearts of pregnant female rats in the experiment.

Materials and methods. Modeling of the effect of cadmium chloride and succinate solutions on the body of the female and indirectly on the course of embryogenesis and heart development in rat embryos was carried out from the first day and throughout pregnancy daily orally through a probe. The experiment was chronic in nature. All pregnant female rats were divided into 4 groups: the first group – control; the second group – isolated injection of cadmium chloride solution at a dose of 2.0 mg/kg; the third group – combined administration of a solution of cadmium chloride at a dose of 2.0 mg/kg and copper succinate at a dose of 0.1 mg/kg; the fourth group – combined administration of cadmium chloride solution at a dose of 2.0 mg/kg and zinc succinate solution at a dose of 5 mg/kg. Operative slaughter and collection of embryonic material took place on the 13th and 20th days of embryogenesis under thiopental anesthesia in accordance with the ethical standards for handling laboratory animals.

Determination of the features of accumulation of cadmium, zinc and copper in the heart of pregnant female rats and embryos was carried out with the help of polyelement analysis by the method of atomic emission with electric arc atomization. Measurements were carried out at the State Enterprise “

Ukrainian Research Institute of Transport Medicine of the Ministry of Health of Ukraine” (Odesa) in accordance with the agreement on scientific and creative cooperation. Atomic emission analysis with arc atomization allows qualitative and quantitative elemental analysis of samples of almost any nature.

Research was conducted in accordance with the principles of the Declaration of Helsinki, adopted by the General Assembly of the World Medical Association (2000), the Convention of the Council of Europe on Human Rights and Biomedicine (1997), relevant provisions of the WHO.

Research results. We carried out polyelement research in two main directions: the first is to determine the degree of accumulation of cadmium, zinc and copper in the hearts of pregnant female rats with an effect on the morphological parameters of the heart; the second is to study the level of accumulation of these elements in embryos.

Analysis of the accumulation of cadmium in the hearts of females on the 13th day of the experiment showed the highest level in the group of combined exposure to cadmium chloride+copper and was equal to 0.1234±0.0117 μg/g, which was 2.3 times higher than the control indicators and 1.2 times higher than the level of accumulation in the group of isolated cadmium administration (0.104±0.0244 μg/g). In the group of the combination of cadmium with zinc succinate, the level of cadmium at this time of the study approached the control indicator and was 0.0858±0.0175 μg/g.

On the 20th day of the experiment, the level of cadmium accumulation increased even in the control group and amounted to 0.0699±0.0033 μg/g. We explain this increase by the fact that the experiment was conducted in a cadmium-laden region of Ukraine. At the same time, the rate of cadmium accumulation in the group of isolated cadmium administration also increased as expected – 0.1656±0.0045 μg/g. The tendency to increase the level of cadmium in the group of combined exposure with copper succinate was rather unexpected. On the 20th day, the level of cadmium in this group was the highest (0.2121±0.0219 μg/g) and exceeded by 1.3 times the indicator in the group of isolated exposure to cadmium chloride, and the control indicators by 3 times (Fig. 1).

Fig. 1. Dynamics of the level of cadmium accumulation (μg/g) in the hearts of pregnant female rats in the experimental groups at both studied periods of the experiment.

An increase in the level of copper in the hearts of pregnant females of all groups on the 13th day of the experimental study was unexpected. In the control the copper level was 8.37±0.32 μg/g, and with the isolated introduction of cadmium, it rose to 20.9±0.54 μg/g, i.e. 2.5 times. That is, the isolated introduction of cadmium chloride leads to a significant increase in the copper level in the hearts of pregnant females already on the 13th day of the experiment. It is interesting that in the group of combined administration of cadmium and zinc, the level of copper also increased by 2 times – 17.7±1.29 µg/g.

On the 20th day of the experiment, the level of copper in the hearts of adult females continued to increase. Thus, in the group of isolated introduction of cadmium, the indicator of copper accumulation exceeded the control by 2.9 times and was 24.5±1.4 μg/g; in the group of combined management of cadmium with zinc – 18.6±1.8 μg/g. In the group of combined administration of cadmium with copper succinate, the high level of accumulation of this trace element was predicted and had no significant significance in comparison.

When determining the level of zinc accumulation in all experimental groups, an increase in this indicator was observed. On the 13th day of the experiment, the highest level of zinc in the hearts of pregnant females was determined in the group of isolated cadmium administration and was 87.9±7.36 μg/g, which was 2.2 times higher than the control values. In the group of combined administration of cadmium with copper succinate, the level of zinc unreliably exceeded the control indicators, and the high level of zinc (78.64±6.76 μg/g) in the group of combined administration of cadmium with zinc is not indicative. On the 20th day of the study, a decrease in the level of zinc in the hearts of pregnant female rats was determined in comparison to the previous period of the study, even in the control group, the level of zinc decreased in comparison to the 13th day of the experiment. We associate this decrease in the level of this trace element with the physiological needs of the pregnant female and the development of the embryos.

Thus, the use of elemental analysis of the hearts of pregnant female rats made it possible to conclude that the introduction of cadmium chloride leads to changes in the level of not only cadmium, but also causes dyselementosis in zinc and copper. The calculation and comparison of the obtained results of the experiment proved the modifying effect of copper and zinc succinates on the degree of accumulation of microelements in the hearts of adult females when they were simultaneously administered with cadmium in an experiment on rats.

The results of the study of copper storage in embryos of different experimental groups showed the following. On the 13th day of the experiment, the level of copper in the embryos of the isolated cadmium exposure group was higher than the control group, but lower than the group of combined administration of cadmium chloride with zinc succinate. Accumulation of copper in all exposure groups (excluding the group of combined administration of cadmium chloride with copper succinate, as it is not representative) compared to the control group indicates a significant disturbance of copper metabolism already on the 13th day of gestation, especially with the combined administration of cadmium and zinc.

On the 20th day of the experiment, we observed a significant decrease in the copper level in the group of isolated exposure to cadmium chloride. This indicator is significantly lower than the control group on the 20th day of the experiment, and also lower than the level of copper in the group of isolated exposure to cadmium chloride on the 13th day, which may indicate a significant antagonistic effect of cadmium on copper exchange processes in rat embryos during chronic administration. At the same time in the group of combined administration of cadmium chloride with zinc succinate we observed the restoration of the amount of copper in rat embryos almost to control values, which can confirm the antagonistic effect of zinc ions in relation to cadmium and the dyselementoses it causes.

When investigating the level of zinc accumulation on the 13th day of the experiment, the increase in zinc content in embryos in the group exposed to cadmium chloride (29.58±12.2 μg/g) compared to the control group (15.3±1,9 μg/g), as well as in the group of combined administration of cadmium chloride with copper succinate (25.7±2.4 μg/g) compared to the control group. At the same time there was no significant difference between the average zinc content in the group of isolated exposure to cadmium and in the group of combined administration with copper succinate. On the 20th day of the experiment a significant difference was noted between the average indicators of zinc content in all groups. Thus, the level of zinc accumulation in the group of isolated administration of cadmium chloride was 34.0±3.3 μg/g, while in the control group it was noted at the level of 27.0±2.1 μg/g. The group of combined administration of cadmium chloride with copper succinate was marked by a decrease in the level of zinc accumulation in embryos (22.0±2.3 μg/g), which is significantly different from both the control group and the group of isolated administration and is the lowest indicator among all groups . This may indicate a significant disturbance in the balance of zinc metabolism in embryos with the simultaneous introduction of cadmium and copper.

The analysis of the obtained results confirms the formation of copper and zinc dyselementosis with chronic exposure to cadmium chloride both on the 13th and 20th day of embryogenesis, which is quite logical, because cadmium is able to overcome the placental barrier and cause dyselementosis of the main divalent cations in embryos rats with chronic administration. At the same time, we observed a pronounced bioantagonistic effect of copper and zinc in relation to cadmium, since the levels of cadmium accumulation significantly decreased in the groups of combined administration, although not to the control indicators.

The results obtained during the experiment reflect the general tendency to accumulate cadmium in various tissues and organs of the rat body. We were interested in the relationship between the distribution and accumulation of cadmium, copper, and zinc in all experimental groups, because there are currently a few data on the combined effect and antagonistic interactions of these elements and they differ significantly.

It was confirmed that the accumulation of cadmium is closely related to the duration of exposure and its level increased in embryos and hearts of female rats at different stages of the experiment. There is a significant difference between the accumulation of cadmium in the embryos and hearts of female rats in the isolated exposure group and the control group. This indicates the widespread distribution of cadmium in the rat body and confirms its ability to overcome the placental barrier [6, 7, 8].

In groups of combined administration, we observed different directions of interaction of cadmium with copper or zinc. Thus, in research groups zinc showed the ability to reduce the negative impact of cadmium on embryogenesis and the heart of a pregnant female. These results coincide with the general findings of bioantagonistic properties of zinc in relation to cadmium ions [9, 10, 11]. In addition, a number of studies indicate that copper can also reduce the negative effects of cadmium on the body of rats [12], however, there is currently very little data on the content of this metal in experimental animals.

Conclusions. The obtained results allow us to make the following generalizations:

  1. When cadmium chloride solution is administered at a concentration of 2 mg/

kg, a different degree of cadmium accumulation is observed in the hearts of pregnant females and embryos, depending on the duration of cadmium administration, as well as the nature of administration: isolated or in combination with copper or zinc succinates.

  1. The isolated introduction of cadmium and in combination with copper succinates reliably reduces the weight of the female heart and the heart mass index in comparison with the control group, while the combined introduction of cadmium chloride simultaneously with zinc succinate increases these indicators almost to the level of the control group, which indicates a significant bioantagonistic the influence of zinc ions in relation to cadmium ions.
  2. Because the cadmium is able to cross the placental barrier, we observe a significant increase in the concentration of cadmium in rat embryos in different exposure groups, as well as significant shifts in copper and zinc content indicators compared to the control group. This confirms data on the ability of cadmium to be actively involved in the metabolism of the embryo and cause copper and zinc dyselementoses.

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