Metabolic processes in the body and bones of experimental animals under conditions of exposure by cadmium and nitrite ions

N. S. Khopta, A. L. Romaniuk, L. Ja. Netchitajlo, A. M. Ersteniuk
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Ivano-Frankivsk National Medical University, 2 Halytska str. Ivano-Frankivsk, 76018, Ukraine

Heavy metals, including cadmium, and also nitrates and nitrites, belong to the most common environmental pollutants. It is known that the condition of bone tissue is determined by the coherence of de- and remineralization processes, the balance of calcium-phosphate metabolism, the content of essential bioelements, and the activity of enzymes that ensure the degree of bone mineral density. The experiment studied markers of bone metabolism in blood plasma and femurs of white male rats under conditions of complex action of cadmium ions and nitrites. Intoxication of animals was carried out for 10 days by administration of the appropriate salt (aqueous solution of NaNO2 with drinking water and intramuscular solution of CdCl2) at a dose of 1/10 LD50 daily once a day. Bone metabolism indicators were examined on the 1st, 14th, and 28th day after the end of toxicant administration. The concentration of total and ionized calcium, magnesium, phosphates, oxyproline, activity of alkaline and acid phosphatase were determined in blood plasma by standardized methods. The content of the bioelements calcium, magnesium, zinc, copper, and toxic cadmium in the femurs was determined using a S-115PK atomic absorption spectrophotometer. Bone mineral density (BMD) was determined by X-ray densitometry. The experiment was conducted in compliance with bioethical requirements. The results of the study showed that under the conditions of the complex action of the studied toxicants, significant changes in the concentration of total and ionized calcium, magnesium, and phosphates occur in blood plasma. The concentration of oxyproline and acid phosphatase activity increase as markers of osteoclast activity. At the same time, alkaline phosphatase activity decreases, indicating inhibition of osteoblast function. In the mineral phase of femoral bones, a decrease in the content of osteotropic bioelements was found against the background of an increase in toxic cadmium. The mineral density of the femurs also decreased significantly, especially in the head and neck areas. The greatest changes were observed on the 14th and 28th days after the introduction of toxicants. The obtained results indicate a violation of calcium-phosphate metabolism and bone tissue remodeling processes in intoxicated rats, in particular, the predominance of osteoclastic resorption processes over osteosynthesis.

Key words: cadmium chloride, sodium nitrite, bone tissue, markers of bone metabolism, osteotropic bioelements, bone mineral density