INFLUENCE OF GENERAL HYPOTHERMIA ON THE BONE MINERAL DENSITY OF THE VERTEBRAL BODIES IN OVARIECTOMIZED RATS

Malyshkina S. V., Nikolchenko O. A., Vyshniakova I. V., Poshelok D. M.

CLINICAL AND EXPERIMENTAL MEDICINE

Scentific article

Skeleton as the most important structure of the mineral metabolism deposits the macro- and microelements that determine bone strength and functional peculiarities. Data that induced hypothermia causes significant changes in the mineral content of rat bone and destructive changes in bone structure are presented in the scientific literature. These changes in bones can lead to the bone strength decrease and increase of the fracture risk. However, we have not found any research work related to the study of bone mineral density (BMD) in ovariectomized rats and without ovariectomy after the induction of hypothermia. The objective of the research was to study the effect of general mild hypothermia on mineral density of the lumbar vertebrae in rats with the modeled ovariectomy. Materials and Methods. 40 female rats aged 6 months were divided into four experimental groups: 1st group – intact (as control group); 2nd group – ovariectomized rats; 3d group – rats with induced hypothermia; 4th group – ovariectomized rats with induced hypothermia. Modeling of ovariectomy in rats was performed by surgical removal of the ovaries under conditions of general anesthesia. Osteopenic changes caused by ovariectomy occurred within for three months. General mild hypothermia in rats was induced by placing the animals in the temperature chamber at –20°C for 5 hours each day within a period of 5 days. Bone mineral density (BMD, g/cm2) in lumbar vertebrae was analyzed using densitometer Explorer QDR W (Hologic) at 1st and 21st days after induced hypothermia. The comparative analysis was conducted by T-test for paired samples to determine the degree of difference data obtained in the experimental groups. Results. BMD in lumbar vertebrae of the intact rats has increased by 10.9 % within interval from 1st to 21st days (from 0,184 ± 0,006 to 0,204 ± 0,005 g/cm2). According to the literature data, peak bone mass in rats is formed in 10-12 months. Ovariectomy in rats negatively affects the BMD in lumbar vertebrae, which was lower compared to intact animals by 10.5 and 13.2% respectively on the 1st and 21st days. BMD in lumbar vertebrae of the rats with induced hypothermia statistically not differs from the intact rats on the 1st and was lower by 14.7% on the 21st days after the exposure to cold. Combined effect of ovariectomy and cold exposure resulted in significant decrease of bone density. BMD in lumbar vertebrae of the ovariectomized rats with induced hypothermia compared to intact rats was lower by 14.1 and 23.1% respectively on the 1st and 21st days, whereas in comparison to rats with induced hypothermia decline was 9.8 and 11.3%. In the literature, there is evidence of communication reduce of vertebral bodies bone mineral density of ovariectomized rats with degenerative changes in the intervertebral discs. Conclusion. Ovariectomy in rats with hyperthermia causes a significant decrease in BMD of lumbar vertebrae which leads to deterioration of the strength characteristics of bone and increased risk for osteopenia, osteoporosis. Prospects for further research. The literature data suggests that the decrease in bone mineral density of the vertebral bodies is a risk factor for degenerative changes in the intervertebral discs, and the study of the structural peculiarities of the intervertebral discs in animals with modeled ovariectomy and hypothermia is relevant.

bone densitometry, vertebral bodies, mild hypothermia, ovariectomy, rats

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«Bulletin of problems biology and medicine» Issue 2 part 1 (128), 2016 year, 60-64 pages, index UDK 611.08:616-001.18:618.11-089.87:611.711.6:616-073.75 ]:599.323