An in vivo and ex vivo investigation of the cellular effects of the heavy metals cadmium and chromium alone and in combination

Abstract

The growth in the industrial sector has caused some unfavourable environmental effects. Heavy metals have become synonymous with industrial pollution due to their toxicological and physiological effects on the ecosystem. This is especially true in South Africa, a country that has a thriving industrial sector and not always the means to correctly dispose of toxic materials, like heavy metals, which then enters the air and water supplies. People living in the areas near the polluted air and/or water are the most affected and not only by one metal at a time, but most likely to a combination of metals. Thus the aim of the current study was to investigate the cellular effects of the heavy metals cadmium (Cd) and chromium (Cr) alone and in combination on liver, pancreas and kidney tissue and human blood by implementing in vivo and ex vivo models, respectively. The in vivo model was implemented successfully over a period of 28 days where male Sprague-Dawley rats received daily dosages of Cd and Cr alone and in combination at a 1000 times that of the World Health Organization’s acceptable water limits. The liver, pancreas and kidney tissue as well as blood was collected from the animals and analysed for histological and ultrastructural alterations, with electron energy-loss spectroscopy. In addition, the blood was evaluated for blood plasma and chemistry levels and ultrastructural analysis with scanning electron microscopy. The blood plasma levels confirmed the presence of the metals in the blood and the blood chemistry levels revealed that the levels of certain liver and kidney tests decreased, indicating that the function of these organs were altered. The histological analysis showed major alterations in the liver and kidney, with minor changes seen in the pancreas, with no fibrosis seen overall. The ultrastructural analysis of the tissue revealed that the metals had some effects on the organelles, as well as bioaccumulated in the organelles investigated. Ultrastructural analysis was also completed on the coagulation system of the animals using scanning electron microscopy, with the erythrocytes, platelets and fibrin networks showing some ultrastructural alterations in all the metal exposed groups. In the ex vivo model, the ultrastructural, confocal and viscoelastic characteristics of human blood after exposure to Cd and Cr alone and in combination was evaluated. The heavy metals affected all the components of the coagulation system, which included an increase in eryptosis, Annexin-V positive signal, platelet activation and spreading as well as significant increase in fibrin fibre thickness. The thromboelastography® analysis, although not statistically significant, indicated that the final clot will probably result in a fragile, less-stable clot, due to changes mainly to the platelets and fibrin networks. In conclusion, Cd and Cr alone and in combination had an effect on the blood enzymes and proteins levels, morphology and ultrastructure of the tissue, thus influencing the function of the liver and kidneys and to a lesser extent the pancreas. The heavy metals also influenced the coagulation system, as it led to fragile, less-stable clots which might lead to diverse cardiovascular diseases.