Журнал «Боль. Суставы. Позвоночник» 2 (18) 2015

Статья опубликована на с. 90

Introduction. The relevance of the research. Bioelectric properties of bone tissue are determined by static and dynamic electrogenesis. Static electrogenesis is causing slowly time–varying electric potentials (EP) in bones which include potentials of resting, growth and regeneration [1, 2].

The aim of this study was to examine age–dependent differences in values and distribution of the EP on the periosteal surface of the femur of young and old rats.

Materials and methods. Studies were performed –using 42 male Wistar rats at the age from 1 to 24 months. Freshly isolated femurs obtained from the pre–anesthetized and decapitated animals served as materials for the study. Femurs were skeletonized and immersed in sodium chloride 0.9% solution. Measurement of EP was performed on electrophysiological device [3]. Ag–AgCl electrodes with agar salt bridges were used in the studies. While measuring, the reference electrode was placed on the distal epiphysis of femur and the measuring electrode was moved along the periosteal surface of bone using a micromanipulator. The measuring electrode was fixed in the following anatomical and topographical areas of femur: the distal epiphyseal–metaphyseal, the distal metaphyseal–diaphyseal, the center of diaphysis, the proximal metaphyseal–diaphyseal and the proximal epiphyseal–metaphyseal.

Results. The negative polarity electric potentials were recorded on the periosteal surface of the rats’ femur. Their absolute values ranged from –0.1… 0.2 to –2.0… –3.0 mV. The distribution of the electric potential magnitude on the bone surface of young and old rats had general patterns. At all ages the maximum values of EP were recorded in epiphyseal–metaphyseal growth plate, and the minimum — in the center of diaphysis. However, the value of EP for older rats was significantly lower than for young ones. It was typical for all anatomical and topographical areas of the femur. The maximum value of the negative potential reached up to –2.96 ± 0.50 mV among 1–2–month old rats. The values of the EP were –2.60 ± 0.22 mV among 3–4–month old rats, and at the age of 14–15 months — 0.61 ± 0.19 mV. The maximum values of the EP did not exceed –0.30 ± 0.09 mV among 18–19–month old rats, and –0.20 ± 0.05 mV among 22–24–month old ones. The most expressed age–dependent differences in the EP magnitude were typical for the epiphyseal–metaphyseal growth plate. It is known that this area of growing bone has the highest rate of metabolic processes. The values of EP in bones epiphyseal plates decreased after their closure among older rats. But it remained higher than in other parts of the femur as a rule.

The maximum differences in the magnitude of EP have reached up to –2.51 mV among young rats, whereas they did not exceed –0.32 mV among old ones. The degree of individual variability values of EP decreased with age. The differences in the EP magnitude in separate regions on the bone surface are also decreased. The maximum dispersion of EP within the group reached up to 1.99–1.85 for young rats. But it was only 0.47 among 14–15–month rats and not more than 0.09–0.06 for old rats.

Conclusion. The effectiveness of static electrogenesis among rats reduces with age. It appeared in decreasing of the EP values on the periosteal bone surface. Differences in the values and distribution of slowly time–varying electric potentials among young and old rats reflected the age–dependent changes in metabolic activity and sates of the physiological remodeling processes in bone tissue.