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Ochilov Komil Rakhimovich, Ph D., associate professor, Head of the Chair of Forensic Medicine and Pathological Anatomy of the Bukhara State Medical Institute, Bukhara, Uzbekistan E-mail: [email protected]
INFLUECE OF IONS OF HEAVY METAL SALT ON BREATHING AND OXIDATIVE PHOSPHORYLATION OF MITOCHONDRIA OF RAT LIVER
Abstract: In experiments in vitro it is established, that heavy metals Co2+ and Cd2+ effectively influence breath and system of mitochondriosome. Ions Co2+ inhibits breath mitochondriosome in conditions V3 and V4, separating oxidizing phosphorylation (OPh). Effect Cd2+ on breath and OPh mitochondriosome differs from action Co2+ and other heavy metals. Thus, Cd2+ in low concentration increases breath mitochondriosome, in high concentration inhibits it. The results received in the present work expand traditional representations about various mechanisms of action of heavy metals on a biopower metabolism of a cell.
Keywords: Ions heavy metals, oxidative phosphorylation, mitochondrios, hepatices.
Salts of heavy metals are present in the environment and are the cause of many chronic diseases of humans and animals [1]. At the heart of the toxic effect of heavy metals on a living organism is the damage of cells and their organelles, accompanied by their functional or structural-functional changes. Among heavy metals, cadmium, cobalt, lead, zinc, aluminum, chromium, etc. are dangerous for life and health.
Cadmium can exert mutagenic and teratogenic ef- Chronic exposure to xenobiotic leads to the forma-
fects on the body, which lead to insignificant destruction tion of structural changes in the cells of the hepatic tis-of the cellular apparatus of the placenta and embryonic sue, which manifests itself in the form of swelling and tissues in the early stages of organogenesis [2]. changes in the shape of the mitochondria, as well as in
The increase in the hepatosomatic index and the pres- the appearance of signs of their biodegradation. The toxic ence of pronounced necrotic changes in the liver is the effect of cadmium contributes to the development of to-main manifestation of the effect ofhigh doses of cadmium tal hydropic dystrophy ofhepatocytes, which sometimes [3]. In the work [4], it was explained that the hepatotoxic turns into balloon dystrophy. In acute intoxication with effect of cadmium leads to the formation of significant cobalt salts, leukocytes, erythrocytes, increased hemo-changes in the biochemical indicators of human blood. globin concentration in the blood; in chronic: leucope-In conditions of chronic poisoning, cadmium leads to de- nia, erythrocytes, increased hemoglobin concentration. struction of the liver and damage to the kidneys, since it At intoxication by salts of metals rupture of membranes has a pronounced hepatoxic and nephrotoxic effect [5]. of erythrocytes of rats is revealed [8].
The toxic effect of cadmium, leading to the devel- The purpose of the work was to study the effects
opment of mitochondrial dysfunction. The growth of of heavy metal salts on breathing and oxidative phos-ischemic events that arise due to damage to the endo- phorylation (OP) of rat liver mitochondria in in vitro thelial cells of the liver vessels leading to the formation experiments.
of hepatocellular trauma [6]. In the experimental study Materials and methods. Mitochondria were iso-[7], it was found that mitochondria and the endoplasmic lated from the liver of rats weighing 150-200 g by the hepatocyte network possess the greatest sensitivity to the method of Schneider's differential centrifugation in a toxic effect of cadmium. isolation medium containing 250 mM sucrose, 10 mM
tris chloride, 1 mM EDTA, pH 7.4. The content of the mitochondrial protein was determined colorimetrically according to the biuret method.
The rate of mitochondrial respiration in the states V3 and V4 was measured with the OH-102 polarograph (Hungary, Radelkis) with an open platinum electrode. The values of DK and ADP / O were determined by the Chance method [5], proceeding from the fact that the amount ofoxygen in 0.5 ml ofincubation medium at 26 ° C is 250 ng - oxygen atom. In the experiments incubation medium (SI) was used: sucrose - 125 mM, KCI - 60 mM, KH2PO4-2.5 mM, succinate - 5 mM, tris-HCl - 5 mM, pH-7.4; additions of ADP to a final concentration of 0.2 mM; concentration of protein M x 3 mg/ml. The rote-none was added to the incubation medium to prevent the accumulation of oxaloacetic acid, a competitive inhibitor of succinate oxidation.
Results and discussion. When studying the effect of cobalt ions on respiration and RP of mitochondria in in vitro experiments, it was shown that Co2+ ions inhibit respiration in the metabolic states of V3 and V4. At the same time, the parameters of respiratory control (DK) and ADP/O decrease. However, there is no complete disconnection of the formatting object. Significant inhibition of respiration and disconnection of the mitochondrial phase of OH is also observed when exposure to higher concentrations of Co2+ (5-10-5M - 10-4M).
It is known that unlike Zn2 +, low concentrations of Co2 + do not affect the respiratory chain, then one of the causes of respiratory depression and separation of OP by Co2 + ions is possibly a decrease in the membrane potential due to an increase in passive permeability for charged membrane particles or a change in the state of CsA-sensitive pores.
According to Professor KT Almatova et al. [9] Co2+ ions are activators of cytochrome c-oxidase and roten-on-sensitive NADH-oxidase system of mitochondrial membranes. These authors showed that the increase in the activity of these enzymes depends on the concentration of CoCl2. Co2 + ions also activate the succinate oxidase systems of the mitochondrial respiratory chain. The authors conclude that the presence of Co2 + ions in the medium leads to significant changes in the electron transport chain of the mitochondria [10, 11].
S. M. Korotkov and co-authors [12] found that the action of Cd2 + ions on respiration and RP Mx is pecu-
liar: relatively low concentrations stimulate respiration in the states V3 and V4, while the coefficients of DK and ADP/O decrease slightly.
Under these conditions, high concentrations of this caution inhibit respiration in both states and lead to complete disconnection of the OB with removal of the DC mechanism. In experiments in vitro, we studied the effect of Cd2+ on respiration and RP of rat liver mitochondria. Cd2+ ions in comparatively low concentrations increased the indices of V3 and V4, however, the coefficients of DK and ADP / O slightly decreased. The addition of Cd2 + to the suspension to a final concentration of1 x 10-5 M also caused simultaneous stimulation of respiration in the V3 and V4 states, while the values ofDK and ADP/O were just below the control level. A further increase in the concentration of Cd2 + in the medium led to respiratory depression.
With an increase in the Cd2 + concentration to 2 x 10-5 M, the mitochondrial respiration in the V3 state was inhibited by 67%. Suppression of respiration was also observed in the V4 state. As a result of marked inhibition, the value of the DC coefficient decreased to 1.61; ADP/O-1.3. At a concentration of Cd2 + 7.5 x 10-5 M, the coefficient of DC decreased to 1, i.e. there was a complete disconnection of the PF with the removal of the DC mechanism.
In our experiments, dithiothreitol (DTT) removes the effect of Cd2 + on respiration and the OB system. It is known that DTT protects thiol groups of mitochondrial membranes. It can be assumed that the effect of Cd2+ on the function of mitochondrial membranes is mediated through thiol groups of membranes.
The mechanisms of action of Cd2+ on respiration and RP of mitochondria are quite complex and attract many researchers. As early as the 1980s, it was shown that Cd2+ increases the permeability of mitochondrial membranes for cations and activates respiration. Higher concentrations of Cd2+ inhibit respiration in the presence of OP disenters.
The effect of Cd2+ on the function of mitochondria depends on its concentration. Apparently, in the presence of high concentrations, the activity of succinate dehydrogenase, cytochrome C oxidase and other enzymes are inhibited, as a result of which respiration is suppressed.
The effect of Cd2 + on respiration is partially removed by heavy metal ions and the classical inhibitor of Ca2+
transport in Mx-ruthenium red, however, the mechanisms of action of these agents have not been fully elucidated.
It should be noted that the effects of Cd2+ on respiration and RP Mx differ from that of Co2+. At higher concentrations, Co2+ does not completely disentangle the OV, while Cd2+ completely disconnects the mitochondrion phase of the OV.
Our investigations carried out in this paper establish that the ions Co2+ and Cd2+ disunite the OP. However, mechanisms of disengagement of OBs by heavy metals have not been finally established. To date, the mechanisms of the action of the uncouplers of PF have been established. All mechanisms and postulates of the action of uncouplers of PF suggest that they facilitate the transition of protons (H+) or other charged particles directly through the mitochondrial membrane.
The motor of the formation of ATP from ADP and inorganic phosphate is just the proton gradient on both sides of the membrane Mx, which is not permeable to H+, supported by biological oxidation reactions. However, the molecules of the uncouplers - protonophores -
can bind H+, and the ionophores some cation and transfer them through the internal membrane, as a result of which a decrease in MP membranes and disconnection of the OB is observed.
Perhaps in our experiments, heavy metal ions interact with mitochondrial membranes and induce passive permeability. As a result, there is a decrease in the membrane potential and separation of the mitochondrion phase of the OH.
Thus, in vitro experiments it has been established that the heavy metals Co2+ and Cd2+ that we study effectively influence respiration and the system of mitochondrial phase. Ions of Co2+ inhibit the respiration of mitochondria in the states V3 and V4, separating the OP. The effect of Cd2 + on respiration and RP of mitochondria differs from that of Co2+ and other heavy metals. In this case, Cd2+ at low concentrations increases the respiration of mitochondria, at high concentrations it inhibits it. The results obtained in this paper broaden the traditional ideas about the various mechanisms of action of heavy metals on the bioenergetic metabolism of the cell.
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