Some Aspects of Lead Exclusion with Excrements from Laboratory Rats in the Experimental Conditions

Contamination of the environment is one of the most important challenges of today's world. Heavy metals are considered to be the most dangerous environmental contaminants. Lead (Pb) is one of the most toxic elements for living organisms. Chronic intake of lead causes numerous severe irreversible disorders. The purpose of the study was to obtain the results on characteristics of the exclusion of a dangerous toxic element, lead, from the organisms of laboratory rats after its oral administration; to determine the lead amount and concentration excreted from the animal body during the experiment; and to study the parameters of this process, including the percentage of this dangerous pollutant excluded from the body of animals, in relation to the volume of the metal administered. Material and methods. The duration of the experiment was 16 days. There were two groups of animals: experimental and control. All animals were placed in individual cages with identical conditions of stay. Individual Pb doses were administered to every animal in experimental group, depending on the weight of the animal, but in equal daily dose, in mcg per 1 mg of body weight. Results and discussion. The volumes of microelements excreted (per 1 g of animal body weight) were calculated. The first peak of Pb excretion in experimental animal was found on the 5th day of the experiment and comprised 0.7 mg per 1 g of body weight. Then there was a decrease in Pb exclusion, and a gradual increase of this index up to 0.4 mcg for the next 10 days. There was a further significant decrease to the minimum values (0.1 mcg) for 11 days and a re-increase to almost 1.0 mcg for 12 days. The amount of Pb exclusion is mainly affected only by the level of the microelement concentration in the faeces, not the amount of the faeces. In order to determine the percentage of Pb that was excreted, a relative indicator was calculated (where 100% was the amount of Pb that was ingested by each animal (5.9 mg on average). The percentage of microelement removal with faeces from the body of experimental animals did not exceed 2.5%. Two peaks of the highest percentage of Pb excretion were recorded. These were 5 and 12 days, which totally coincided with the maximum concentration of pollutant and the amount of faeces. The correlation with the micronutrient concentration in faeces was extremely high, with r = 0.98. Conclusions. Indicators for the elimination of lead with faeces per day in experimental animals exceeded the same indicators in the control group, which corresponds to the conditions of artificial intake of the metal into the body of the rats in the experimental group. The amount of Pb toxicity per day was more influenced by the concentration of the trace elements in the faeces (in control animals r = 0.90, and in the experimental ones r = 0.98), but not by the amount of faeces. The percentage of excretion of trace elements from the body of experimental animals was low. The relative indicator varied rather broadly throughout the experiment. Some part of the toxicant was excreted from the body of animals with urine, but significant amount of Pb was accumulated in the body.