THE EFFECT OF HYPERTHERMIC STRESS AT DIFFERENT DEVELOPMENTAL PERIODS IN THE WHITE RAT ON DNA CONTENT IN ANDRENAL GLANDS

Abstract

The influence of high ambient temperature on biochemical processes in homeothermic organisms is the subject of interest in a large number of researches from different disciplines of biology and medicine. Namely, during a long-term stay in conditions of high external temperature, the organisms react adequately in order to maintain the internal homeostasis. At the same time, processes at the level of nervous, endocrine, metabolic and water homeostasis play a major role. High external temperature has a negative impact in all developmental stages of the white laboratory rat, and all research confirms the teratogenic effect of hyperthermia on their organs and glands. Regardless of the experimental treatment, until the 50th day of life, there is a constant increase in the mass of the adrenal glands, which is due to the continuous growth and development of the young organism, but the dynamics of the growth and development of the adrenal glands in the different experimental groups clearly deviates in relation to the control group, depending on the duration of the exposure to the high external temperature. The subject of our interest in this paper was the DNA content in the adrenal glands after exposure to high ambient temperature. For this purpose, we used white Wistar laboratory rats as experimental animals and they were divided into five groups. The first control group, which during the entire experiment, pregnancy, lactation and until the 50th day of the post-lactation period, we fed in a standard way, food and water as desired and stayed at room temperature, the second group of animals exposed for two hours a day to 40 °C during pregnancy, and after hatching they stayed at room temperature, the third group was exposed for 2 hours a day to 40 °C during lactation, the offspring and the mother were placed in a thermostat at 40 °C, the fourth group was exposed after two hours per day at 40°C during post-lactation and the heel was exposed for 2 hours per day at 40°C from birth to day 50 of life. The principle of the method for determining DNA in tissue consists in the strictly specific connection of indole with deoxyribose, for which a strongly acidic environment and high temperature are necessary, while the intensity of the color of the solution, which comes from the formed yellow-brown complex, is directly proportional on the concentration of deoxyribose ie. of DNA content. The results showing the concentration of DNA in 100mg of adrenal glands, that is, the relative content of DNA, also confirm the results obtained for the absolute content of DNA in the tissue of the adrenal gland. The studies carried out on the effect of intermittent exposure to a high external temperature of 40°C at different developmental stages in the white rat on the DNA content in the adrenal glands suggest that the high ambient temperature applied during pregnancy has no or very little effect on the examined parameter, while exposure during lactation causes an increased mass of the adrenal glands, which also results in an increased content of DNA in them. In the post-lactation period, the value returns to a level close to the control. This increase in DNA content in the adrenal glands is probably due to the increased activity of the hypothalamus-pituitary-adrenal axis in the conditions of hyperthermic stress.