Features of Rats' Skeleton Formation under the Influence of Insulin

One of the fundamental problems of modern anatomy is the problem of determining regular changes in the bone system under the influence of the exo- and endogenous factors of the organism. The purpose of our study was researching the features of rat's bones growth and morphological transformations after introducing exogenous insulin. Material and methods. The experiment was carried out on 120 white sexually immature rats (30-35 days old, with the initial weight of 50-60 g). The animals were divided into groups depending on the type of substances introduced and the duration of the experiment. The first (control) group was made up of contact rats, which got distilled water in the volume equal to the dose of insulin. The second group consisted of animals, which were injected with insulin in the average experimental dose – 3 U/kg. At the end of experiment, the rats were killed by decapitation under ethereal anesthesia with the simultaneous taking blood for study. We used the following methods of investigation: osteometry, histomorphometry, biochemical and biomechanical analysis, NMR relaxation of tissue fluid protons. The obtained data were processed by mathematical statistical methods using the standard program package (Microsoft Office 2003, Microsoft Excel 2003, Statictica 6.0). Results and discussion. We observed increasing of the proliferative activity of the tibia epiphyseal cartilage with a tendency to increase their transverse and longitudinal dimensions under the influence of exogenous insulin at the initial stage of the experiment (first week). Changes of spin relaxation indicated a delayed proton exchange between free and hydrated fractions of water in bones. Further introduction of insulin (for 30 days) led to a gradual narrowing of the epiphyseal cartilage in comparison with the control parameters. In addition, the rate of the tibia longitudinal growth was slowing down at the background of increased activity of transverse size growth. An increase of the protons relaxation time in the tissue fluid led to a slight hyperhydration of all investigated bones. The increase in the mineral substances content, combined with the increase of the Ca/P coefficient, took place at the beginning of the experiment and reached the maximum indexes after 14 days of introduction of insulin. This process can be explained by the hyperinsulinemia. Further introduction of the beta-cells hormone led to a reorganization of the carbohydrate and other types of metabolism, which was accompanied by a decrease in the level of mineral substances in the investigated bones. The investigation of the tibia macronutrient composition showed the same changes in calcium level at the background of not-changed level of phosphorus. Conclusions. Despite the initial increase of the humerus density characteristics, they became less then control indexes at the end of the experiment. The long-term administration of insulin possibly led to insulin intoxication, which contributed to the disturbance of the exchange regulatory mechanisms of phosphoric and calcium homeostasis.