Somatostatin modulates T cells development in adult rat thymus.

It is well known that somatostatin modulates thymic functions, such as binding to receptors. In order to elucidate the influence of somatostatin on the thymus architecture and the T cells maturation, young adult male rats were treated with somatostatin-28. The results showed that somatostatin-28 decreased thymus weight and cellularity, probably due to alterations in the thymic morphometric parameters. Our results also demonstrated that SRIH treatment reduces number of cells with undetectable alphabetaTCR and cells with low expression of alphabetaTCR, while the number of TCRalphabeta(hi) cells remains approximately the same as the values obtained from the control rats. Besides, in the least mature thymocytes (DNTCR TCRalphabeta(-)) and among the most mature the SPCD4 TCRalphabeta(hi) subset remained unaltered, while SPCD8 TCRalphabeta(hi) decreased. At last, it should be noted that SRIH treatment increases DN thymocytes subsets expressing TCRalphabeta(low/hi) (TCRalphabeta(+)). These results suggest that somatostatin-28 induces reshaping of T cells maturation and, at least partly, contributes to thymic weight loss, through the modulation of the complex neuroendocrine-immune network.

Exposure to forced swim stress alters morphofunctional characteristics of the rat thymus.

The aim of this study was to investigate whether chronic stress, induced by repeated daily swimming during 21 days, alters the morphofunctional parameters in the thymus of adult rats. Our results showed that chronic stress reduced thymus mass, total number of thymocytes, volume of the thymus compartments and numerical density of thymocytes within thymus inner cortex and medulla. However, the percentage of apoptotic cells and the level of corticosterone were significantly increased. The percentages of CD4-CD8-TCRalphabeta(low/high) and CD4-CD8+TCRalphabeta(-)thymocytes were significantly increased, while the percentage of the least mature CD4+CD8-SP TCRalphabeta(-) thymocytes was significantly decreased. These results show that recurred swimming procedure induces thymus hypotrophy and elevated percentage of DN TCRalphabeta(+) cells.

Changes in the thymus of peripubertal rats induced by centrally applied somatostatin-28.

The aim of this study was to investigate the effects of centrally applied somatostatin-28 on morphometric characteristics of the thymus, the thymocyte subpopulations, as well as, on apoptosis and phases of cell cycle in thymocytes. For this purpose, peripubertal male rats were cannulated intracerebroventriculary and treated with repeated, nanomolar concentrations of somatostatin-28 (experimental group) or saline (control group). Animals were sacrificed and their thymuses were used for the analysis of thymocyte subpopulations, cell cycle and apoptosis by flow cytometry and for the evaluation of morphometric parameters by stereological analysis. Our results showed that somatostatin-28 caused decrease of the thymic mass and volume, as well as total thymocytes number. Stereological analysis revealed volume decrease of thymic cortex and medulla accompanied with cellularity decrease. Somatostatin in the deeper cortex decreased the number of thymocytes, per volume unit, while in outer cortex raised their number. A significant increase in the percentage of double-negative and both single-positive thymocyte subpopulations, in parallel with a diminished percentage of double-positive cells was found. The cellularity of double-positive and single-positive thymocyte subpopulations was decreased. Somatostatin-28 treatment augmented the percentage of apoptotic cells, while the percentage of the cells represented in phases of cell cycle was reduced. These results suggest that somatostatin-28 induce thymus hypotrophy as result of decreasing cortex and medulla volume and cellularity. Changes in the percentage and cellularity of thymocyte subpopulations and numerical density of thymocytes in outer and deeper cortex, indicate that somatostatin-28 evoked disturbance in transition of double-negative to double-positive thymocytes.