Features of Spleen Development in Newborn Rats Exposed to Endocrine Disrupter Dichlorodiphenyltrichloroethane during the Prenatal Period.

The development of the spleen in newborn male Wistar rats exposed to low-dose endocrine disruptor dichlorodiphenyltrichloroethane during the prenatal period was studied. Histological examination of the spleen revealed a more active development of periarterial lymphoid sheaths and lower granulocyte content in the organ. Cytofluorimetry showed a significantly lower content of B cells. Thus, low-dose exposure of the endocrine disruptor dichlorodiphenyltrichloroethane on the developing organism during the prenatal period induced changes in spleen morphogenesis resulting in extensive development of lymphoid formations and a lower intensity of lymphocyte and granulocyte differentiation.

Regulation of Morphogenetic Processes during Postnatal Development and Physiological Regeneration of the Adrenal Medulla.

Regulation of morphogenetic processes during postnatal development of the rat adrenal medulla was studied. Termination of the adrenal medulla growth was found to be associated with decreased chromaffin cell proliferation, activation of canonical Wnt-signaling pathway, and enhanced expression of Sonic Hedgehog ligand. Analysis of transcription factors associated with pluripotency revealed increased percentage of Oct4-expressing cells by the end of medulla growth and no signs of Sox2 expression. All the cells demonstrating activation of Wnt-signaling and expression of Oct4 and Sonic Hedgehog were found to be highly differentiated chromaffin cells actively producing tyrosine hydroxylase. These findings allow considering the formation of the cell pools for dedifferentiation as a putative mechanism for physiological regeneration of the adrenal medulla.

Changes in Secretion of the Thyroid and Pituitary Glands with a Gradual Decrease in Deuterium Body Content.

We studied changes in the secretion of thyroid hormones and pituitary thyroid-stimulating hormone (TSH) in young mature male Wistar rats during gradual decrease in deuterium body content. The rats received deuterium-depleted water ([D]=10 ppm) instead of tap water for 21 days. As soon as after 1 day, an increase in the secretion of thyroid hormones was recorded. On day 14, secondary hypothyroidism due to a sharp decrease in TSH secretion by the pituitary gland was found. By day 21, secretion of the thyroid hormones increased, and the reciprocal dependence between the concentrations of thyroid hormones and TSH was restored. Thus, the thyroid gland showed a higher sensitivity to a decrease in the deuterium content in the body than the hypothalamic-pituitary complex. The second difference was in type of response: activation of the secretory processes in the thyroid gland and a transient decrease in the secretory activity of pituitary gland thyrotropes to a decrease in deuterium content.

Changes in the Expression of Transcription Factor Oct4 during Postnatal Development of Adrenal Medulla.

We analyzed the expression of the transcription factor Oct4 in the chromaffin cells during the postnatal development of the adrenal glands in rats. Single Oct4+-chromaffin cells with nuclear localization of the protein were found in the medulla, and their number increased in parallel with a decrease in the proliferative activity of cells. In postnatal development, 100% of chromaffin cells demonstrated high expression of tyrosine hydroxylase, which attested to their differentiation and functional activity. It was found that all Oct4+ cells were differentiated chromaffin cells. An increase in the pool of Oct4-expressing cells after the completion of organ growth suggests the formation of a potential source for the physiological and reparative regeneration of the adrenal medulla.

Reactive Alterations in Thymic Lymphocytopoiesis to Short-Term Decrease in Deuterium Content in the Body.

We studied changes in thymic lymphocytopoiesis induced by a short-term decrease in deuterium content in the body. The experiment was performed on adult male Wistar rats receiving water with lower deuterium content [D]=10 ppm. Increased relative weight of thymus was found after 24 h of consumption. Flow cytometry revealed higher percentage of undifferentiated cells and mature T cells, especially cytotoxic T cells. Hence, lymphocytopoiesis in the thymus is highly sensitive to short-term decrease in deuterium body content. A decrease in the content of deuterium stimulates proliferation of lymphoblasts in the thymus and slows down migration of differentiated T cells. Enhanced generation of cytotoxic T cells under these conditions attests to the role of deuterium in selection of double-positive thymocytes. The revealed shifts are reactive, and their pattern can change later, which requires further research.

Mechanisms of Suppression of Epinephrine Production in Rats by Low-Dose Developmental Exposure to DDT.

We studied the mechanisms underlying decreased production of epinephrine by adrenal glands in rats developmentally exposed to endocrine disruptor DDT was performed on the basis of assessment of morphology, fine structure, and function of the adrenal medulla and medullary cells. It was found that the main mechanisms of disruptive action of DDT leading to a decrease in epinephrine secretion into systemic circulation are a decrease in the growth rate of the adrenal medulla, a decrease in the number of mitochondria in adrenal cells, especially under the outer cytoplasmic membrane, destructive changes in mitochondria, and a progressive decrease in the synthesis of tyrosine hydroxylase. The decrease in the number of mitochondria and suppression tyrosine hydroxylase synthesis in adrenal cells predominate during the pubertal period, while slowdown of the growth of the adrenal medulla and progressive decrease in the synthesis of tyrosine hydroxylase seem to be the most evident mechanisms after puberty.

Impact of Reduced Deuterium Intake on Thermoregulation.

The role of stable hydrogen isotopes in the thermoregulation and its regulation is poorly studied. We analyzed fluctuations in body temperature and changes in thermoregulation parameters in mice under conditions of reduced deuterium intake. The study was performed on male C57BL/6 mice that consumed water with a low (10 ppm) and normal (146 ppm) deuterium content. In 7 days, fluctuations of body temperature, locomotor activity, and oxygen uptake were assessed. Deuterium depletion in the body reduced the mean value of minute fluctuations of body temperature and the mean spectral density of minute fluctuations in body temperature in the 2-20-min periods. This attested to a stabilizing effect of deuterium depletion on the rhythms of body temperature fluctuations, without significant shifts in the thermogenesis parameters. Thus, drinking water with reduced deuterium content makes them less sensitive to external influences.

Response of Pituitary-Thyroid Axis to a Short-Term Shift in Deuterium Content in the Body.

We studied functional changes in rat pituitary-thyroid axis after a short-term shift in deuterium body content. Male Wistar rats consumed deuterium-enriched (500,000 ppm) or deuterium-depleted water (10 ppm) for 24 h. Rats of both experimental groups demonstrated elevated concentration of bound with transport proteins thyroxine and reduced level of thyroid-stimulating hormone in serum. No changes in the rate of thyroxine conversion to triiodothyronine were found. Thus, both the increase and reduction of deuterium body content produced similar changes in the function of the pituitary-thyroid axis with primary affection of the thyroid gland, indicative of its higher sensitivity to shift in deuterium levels.

Low-Dose Exposure to Endocrine Disruptor Dichlorodiphenyltrichloroethane (DDT) Affects Transcriptional Regulation of Adrenal Zona Reticularis in Male Rats.

The study examined transcriptional regulation of adrenal zona reticularis development in male Wistar rats exposed to low doses of endocrine disruptor dichlorodiphenyltrichloroethane (DDT) prenatally and postnatally. At pubertal age, zona reticularis demonstrated a retarded growth with a low proliferative activity of its cells. At this age, zona reticularis was characterized with overexpression of ß-catenin by steroid-producing cells; a high percentage of cells with membrane and cytoplasmic localization of ß-catenin, and reduced number of cells with nuclear ß-catenin attesting to insufficient activation of Wnt signaling. Expression of transcriptional factor Oct4 by reticularis cells was down-regulated indicating their diminished proliferative potency. No significant alterations in Sonic Hedgehog expression were observed. Thus, DDT-provoked disorders of transcriptional regulation result in abnormal development of zona reticularis thereby disturbing sexual maturation in males.

Ultrastructural Mechanisms of Impaired Aldosterone Synthesis in Rats Exposed to DDT during Prenatal and Postnatal Development.

The study is aimed at elucidation of ultrastructural mechanisms underlying impaired aldosterone synthesis by glomerulosa cells in Wistar rats exposed to low doses of endocrine disrupter DDT during prenatal and postnatal development. Analysis of rat zona glomerulosa histology and function during the pubertal and postpubertal periods showed that exposure to endocrine disrupter DDT disturbs its development and reduced the production of aldosterone. Electron microscopy showed that changes in the aldosterone synthesis are related to impaired reorganization of the mitochondrial apparatus, one of the leading factors in the regulation of steroidogenesis, in glomerulosa cells in DDT-exposed rats during puberty.

Changes in Histophysiology of the Adrenal Medulla in Rats after Prenatal and Postnatal Exposure to Endocrine Disruptor DDT.

We studied histophysiology of the adrenal medulla in adult (70-day-old) male Wistar rats developmentally exposed to low doses of endocrine disruptor DDT. It was found that exposure to DDT during the prenatal and postnatal ontogeny decelerated the development of the adrenal medulla and reduced the synthesis of tyrosine hydroxylase, the rate-liming enzyme of catecholamine synthesis, in chromaffin cells, which led to a decrease in epinephrine secretion into the blood.

Development of Proliferative Response of Thymic Lymphocytes to T-Cell Mitogen in Rats Exposed to Endocrine Disrupter DDT during Ontogeny.

We studied the formation of proliferative response of thymic lymphocytes to T-cell mitogen in rats exposed to endocrine disrupter DDT during prenatal and postnatal ontogeny. Developmental exposure to the endocrine disruptor was found to attenuate proliferative response during puberty and adulthood due to maintenance of higher proliferation rate of thymic lymphocytes in comparison with age-matched controls. Insufficient proliferative response to mitogens in rats developmentally exposed to the endocrine disrupter increases the risk of impairment of cell-mediated reactions of adaptive immunity.

Morphological and Cytophysiological Changes in the Adult Rat Adrenal Medulla after Prenatal and Postnatal Exposure to Endocrine-Disrupting DDT.

The aim of the investigation was to study morphological and cytophysiological changes in the adult rat adrenal medulla after prenatal and postnatal exposure to endocrine-disrupting chemical dichlorodiphenyltrichloroethane (DDT). MATERIALS AND METHODS: The experiment was carried out on male Wistar rats (n=30). The rats were exposed to low doses of DDT during prenatal and postnatal development (n=10) and during postnatal development (n=10) only. The average daily intake of DDT by rats was 3.30±0.14 µg/kg. The control (n=10) and experimental animals were sacrificed at the age of 10 weeks (post-puberty), when rat adrenal glands reached their maximum development. Histological samples of the equatorial sections of the adrenal glands were prepared. The adrenal medulla was studied using light microscopy and computer morphometry. Immunohistochemistry was performed to evaluate tyrosine hydroxylase expression in chromaffin cells. Plasma epinephrine content was measured using enzyme-linked immunosorbent assay. RESULTS: Postnatal exposure of rats to low doses of the endocrine disruptor was found to interfere with adrenal medulla development and cytophysiology of chromaffin cells. Prenatal and postnatal exposure resulted in more profound delay in adrenal medulla development of adult rats as compared to the values of rats exposed postnatally, which was manifested by reduced area of the adrenal medulla and reduced total area of chromaffin cells in its section. Postnatal exposure is manifested by more significant functional disorders including decreased synthesis of tyrosine hydroxylase enzyme in the cytoplasm of chromaffin cells and elevated number of tyrosine-hydroxylase-negative cells in the medulla section, leading to a decrease in plasma epinephrine concentration. CONCLUSION: Exposure to low doses of DDT in the early stages of development leads to morphological and cytophysiological changes in the adult rat adrenal medulla and, therefore, reduced functional activity of chromaffin cells, which allows considering the endocrine disruptor DDT a potential risk factor disrupting the function of the neuroendocrine system.

Effects of low-dose dichlorodiphenyltrichloroethane on the morphology and function of rat thymus.

The effect of low-dose dichlorodiphenyltrichloroethane on the function of the immune system is a serious problem because of wide use of this pollutant. We studied the morphological and functional changes in the thymus of rats receiving low-dose dichlorodiphenyltrichloroethane for 6 and 10 weeks. Histological studies detected changes characterized by lymphocyte and reticuloepitheliocyte death, progressing with increase of dichlorodiphenyltrichloroethane dose, and a decrease of the thymocyte proliferative activity. The results of comparative analysis of changes in the thymuses of rats in experimental and control groups during different periods of the study indicated that low-dose dichlorodiphenyltrichloroethane promoted earlier onset of age-specific involution and caused a dose-dependent acceleration of these changes.