Morphofunctional organization of somatostatin-synthesizing delta-endocrinocytes of pancreatic islets under experimental conditions

Somatostatin-synthesizing delta-endocrinocytes constitute a minor but functionally important population of pancreatic islets that exert paracrine regulation of insulin secretion by beta-cells and glucagon secretion by alpha-cells. The quantitative and functional remodeling of the delta-cell compartment may be of substantial importance in the endocrine pancreas under conditions of experimental diabetes mellitus (DM), hypoxic training, and hereditary arterial hypertension (AH). Aim. To determine the quantitative parameters of the morphofunctional organization of somatostatin-synthesizing endocrinocytes in rat pancreatic islets under conditions of experimental diabetes mellitus, intermittent exogenous hypoxia, and hereditary arterial hypertension. Materials and methods. The study was conducted on white Wistar rats and spontaneously hypertensive rats (SHRs). Experimental DM was induced by injection of streptozotocin. Intermittent hypoxic exposures were performed in a pressure chamber. Immunofluorescence detection of somatostatin, insulin, and glucagon in sections of pancreatic tissue was done, followed by digital morphometric analysis in ImageJ. Statistical group comparisons were completed via Student’s t-test. Results. In streptozotocin-induced DM rats, total islet endocrinocyte numerical density decreased compared to intact controls (p < 0.05), the delta-cell population was reduced (p < 0.05), and the relative somatostatin immunoreactive area in the pancreas decreased (p < 0.05). In SHRs with hereditary AH, an even more pronounced decrease in the number of delta-endocrinocytes was seen and the relative somatostatin immunoreactive content was lower. In rats subjected to intermittent hypoxia, total endocrinocyte numerical density did not differ significantly from controls; however, the delta-cell population decreased and somatostatin immunoreactive content declined vs. controls. Conclusions. Streptozotocin-induced type 1 diabetes mellitus caused a twofold decrease in the total number of endocrinocytes, including delta-cells, as well as a reduction in the somatostatin immunoreactive content in the pancreas. Hereditary hypertension in SHRs was associated with an approximately threefold decrease in the total number of pancreatic endocrinocytes and an eightfold reduction in the delta-cell population; additionally, the somatostatin immunoreactive content was 21 % lower (p < 0.05) than in animals with diabetes. Intermittent hypoxic training produced a threefold reduction in the delta-cell population and a 30 % decrease in the somatostatin immunoreactive content, while the total number of endocrinocytes remained at the control level.