Dynamics of connective tissue metabolites in the blood of rats of different age under hypokinesia
Authors: Morozenko D. , Leontieva F. , Gliebova K. 
Published: April 2021

Topicality. Hypokinesia is a condition of insufficient motor activity of the body with limited pace and volume of movement, and is currently the fourth leading cause of endemic death in the world. It is known that hypokinesia can affect the metabolism of components of bone and cartilage, which is the basis for the development of pathological processes, but there are no biochemical markers of this process in the literature. Thus, currently, there is insufficient number of experimental scientific works devoted to the study of biochemical parameters characterizing the state of the connective tissue in the experiment to assess the impact of hypokinesia on the body, and this fact determines the relevance of the study.
Aim. To study the dynamics of the main metabolites characterizing the state of the connective tissue in the blood serum in hypokinesia in rats of different ages.
Materials and methods. The studies were performed on 42 white male rats aged 3 and 12 months, kept in the vivarium of the Sytenko Institute of Spine and Joint Pathology National Academy of Medical Sciences of Ukraine, Kharkiv. The conditions of hypokinesia were reproduced using a specially designed device that limited the mobility of the animal without disturbing the ventilation of the body. Animals were removed from the experiment by decapitation in Day 7 and 30 of immobilization under thiopental anesthesia. The content of sialic acids in the serum was determined by the Hess method, chondroitin sulfate – by Nemeth-Csoka method modified by L. I. Slutsky, the fractional composition of glycosaminoglycans (GAG) – by the reaction with resoquine.
Results and discussion. In the study of the rat serum, it was found that in intact animals of 3 and 12 months of age the content of sialic acids was different; it was 2.94 ± 0.16 and 1.98 ± 0.09 mmol/L, respectively. After 7 days of hypokinesia, their concentration in young animals did not change, but in older animals, this figure increased. By Day 30, the serum sialic acid levels suddenly increased compared to intact animals. In animals of 12 months of age, the concentration of sialic acids in the blood serum increased by both Day 7 and Day 30 of hypokinesia, especially at the end of the experiment. Hypokinesia also showed a significant increase in serum concentrations of chondroitin sulfates on Day 7 of the experiment in animals of both age groups. At the same time, the level of these metabolites on Day 30 was at the same level. In young rats on Day 7 the fraction of GAG remained unchanged, but on Day 30 there was a significant decrease. During this period, the second fraction of GAG increased. In animals aged 12 months on Day 7 and 30, the content of most GAG fractions was lower than the values characterizing the fractional composition of GAG in intact rats.
Conclusions. Thus, the determination of sialic acids, GAG fractions and chondroitin sulfates in the serum can be presented as a set of biochemical tests to assess disorders of the connective tissue metabolism while limiting the motor activity of the body. It has been found that the 30-day hypokinesia causes significant disorders of the connective tissue, and it is reflected in changes in the biochemical parameters of the serum of experimental rats.