Lead Effects on Some Excretion Indicators of Laboratory Rats under Experimental Conditions

Contamination of the environment is one of the most important and urgent problems of today's world. Heavy metals are considered to be the most dangerous environmental contaminants that are polluted into the environment in large volumes, primarily as a result of industrial activities. Lead is one of the most dangerous microelements for living organisms. This toxicant can be accumulated in animals and humans to significant levels. Chronic intake of lead causes numerous severe irreversible disorders. The main purpose of present research was to study the specific and quantitative tendencies in excretory withdrawal of lead from the body of laboratory rats after oral intake of the metal. Precise amounts of metal in the excretions in experimental and control groups were determined. The concentrations of the pollutant were measured, and the correlations between the various components of toxic pollution and lead concentration were found. Objects and Methods. The duration of the experiment was 16 days. During the investigation, two groups of animals were used, one of which was experimental, and the other – control group. All animals in both groups were placed in individual cages with identical conditions. Individual Pb doses were administered to every animal in experimental group, depending on the weight of the animal, but equal daily dose in mcg per 1 mg of body weight was administered to all experimental animals. Results and its discussion. The research demonstrated that the volume of excretions per 1 g of body weight of the animals were rather high in both experimental and control groups. Throughout the experiment, the volumes for the animals in experimental group prevailed over those for control animals. During the first week of the experiment, slight decrease in the number of animal excretions in both groups was registered. This may indicate depression of some physiological parameters of animals in the experimental settings. During the second week of the experiment (second half of the experiment), an increase in the volume of excretions was found, compared with the beginning of the experiment. This may indicate a slight improvement in animal condition and their adaptation to the experimental settings, accompanied by the intensifying in the withdrawal of the lead as environmental pollutant. However, such assumptions may be valid only for the experimental group of animals. Average number of excretions (per 1 g of body weight of the animal) were 37,1 ± 7,6 mg for the experimental group, and 29,7 ± 9,7 mg for the control group. These figures predominately support an increase in excretions in animals of the experimental group, perhaps due to adaptive response directed to the remove excess of harmful pollutant out of the body. We also determined concentrations of some of the most common trace elements, both biogenic and toxic. To investigate possible relations between Pb concentration and the content of other elements, correlation coefficients were determined. Correlations between the Pb and concentrations of Mn, Cu, Zn were found in experimental animals, while those relations in control animals were only minor. This suggests a significant relation between the accumulations of various heavy metals. Regarding another dangerous pollutant, Cd, the correspondent correlation throughout the experiment was insignificant (r = 0,51). However, it greatly increased and became significant, when only the second half of the experiment was taken into account (the second week, starting from the 9th day). In this case the correlation coefficient was as high as 0,93, indicating almost synchronous processes in the changes in the concentrations of these dangerous pollutants.