Changes in the morphometric parameters of the peripheral endocrine glands and microstructure indicators, phase composition of the biomineral of the regenerating tibias after long-term exposure to sodium benzoate

I n t r o d u c t i o n. Sodium benzoate is a preservative widely used in the food industry to increase the shelf life of food products. However, its genotoxic, hepatotoxic and nephrotoxic properties have been established, which requires further study of its effects on the body.

A i m. To study the effect of a 60-day exposure to sodium benzoate on the structure of the thyroid C-cells, the main parathyroid cells and the spongiocytes of the adrenal zona fasciculata, taking into account changes in the microstructure and phase composition of the biomineral of the regenerating tibias amid modeling a mechanical injury.

M a t e r i a l s a n d m e t h o d s. One hundred and twenty albino mature male rats were divided into four groups (30 animals in each group). Animals of groups 1 and 2 were exposed to sodium benzoate for 60 days at doses of 500 and 1000 mg/kg, after which a defect in the tibias was simulated. In group 3, instead of sodium benzoate, the animals were injected with saline solution. In group 4, rats received saline without simulating the tibial injury. The study of changes in the cytomorphometric parameters of the thyroid C-cells was carried out using electron microscopy on the 3rd and 24th days after defect modeling. The study of the morphometric parameters of the main parathyroid cells and spongiocytes of the adrenal zona fasciculata was carried out by light microscopy on days 3, 10, 15, 24, 45, and the indicators characterizing the microstructure and phase composition of the biomineral of the regenerating bones were studied by X-ray diffraction analysis at the same time points.

R e s u l t s. In group 1, the area occupied by euchromatin in the nuclei of C-cells significantly decreased compared to group 3 on the 24th day by 21.13%, and in group 2 on the 3rd and 24th day – by 5.83 and 16.29%. In groups 1 and 2, on the 3rd and 24th day, the ratio of euchromatin and heterochromatin areas was less by 2.65, 22.25 and 6.69, 17.69%, the diameter of secretory granules – by 7.47, 15.43 and 8.92, 16.00%. The number of nuclei of the main parathyroid cells per area unit decreased significantly only in group 2 from the 3rd to 24th day by 3.96, 3.34, 3.68%, and the functional activity index decreased on the 3rd day by 6.34%. The number of spongiocyte nuclei per area unit in the zona fasciculata decreased significantly in both groups from the 3rd to 45th day – by 2.87, 2.40 and 5.57, 3.91%. In the 1st group, the index of functional activity of spongiocytes was lower only from the 3rd to 15th day by 7.20, 6.78, 4.54%, and in the second group – in all time points by 10.73 and 7.23%. In the biomineral of the regenerating tibias in rats of group 1, a significant increase in the size of unit cells along the c axis was revealed on the 15th and 24th days by 0.23 and 0.17%. In group 2, the increase in the size of unit cells along the a axis was significant from the 15th to 45th day by 0.28, 0.15, 0.13%, and the increase in the size of the unit cells along the c axis was significant from the 10th to 45th day by 0.18, 0.23, 0.21, 0.12%. In same groups, a significant positive correlation was found between such parameters as the number of nuclei of the main parathyroid cells, spongiocytes of the zona fasciculata and the size of unit cells along the a, c axes, the percentage of whitlockite, and the correlation between the parameter “ratio of the areas of euchromatin and heterochromatin in the C-cell nuclei” was positive on the 3rd day and negative on the 24th day.

C o n c l u s i o n. The morphofunctional state of C-cells, main parathyroid cells and spongiocytes of the zona fasciculata is dose-dependently inhibited by the previous 60-day administration of sodium benzoate. This is accompanied by alteration of compensatory and restorative processes during reparative osteogenesis. Using the correlation analysis, relationships of varying strength and direction were found between changes in the morphometric parameters of the endocrine glands and the microstructure of the regenerating bones.

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