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Superoxide dismutase reduces islet microvascular injury induced by streptozotocin in the rat
M Enghofer1, K H Usadel, O Beck
1Department of Medicine I, Johann Wolfgang Goethe University, Frankfurt am Main, Germany.
Abstract:
Intravenous administration of streptozotocin (STZ) leads to permanent diabetes mellitus in rats. We investigated the possible role of islet microcirculatory changes and free radical formation in this animal model. In vivo fluorescence microscopy was performed for 4 h after administration of STZ. Vascular permeability, capillary blood flow, and endothelial leukocyte adhesion were measured in endocrine and exocrine pancreatic tissue. The earliest microcirculatory event was an increase in vascular permeability in pancreatic islets, with a peak 1 h after STZ administration. The difference between islet and exocrine tissue light intensity was +15.8 +/- 5.6% at t = 60 min. Islet blood flow velocity significantly decreased after 3 h, whereas blood flow in the exocrine pancreas was not affected. Complete stasis of islet blood flow was observed only in rats receiving STZ. Neither increased leukocyte adhesion to islet vascular endothelium nor ischemia-reperfusion phenomena were observed. Prophylactic administration of the radical scavenger superoxide dismutase prevented STZ-induced damage to the islet microcirculation in the initial phase of this model. We conclude that STZ leads to severe microcirculatory disturbances within pancreatic islets in rats. Apparently, these changes are mediated at least in part by free oxygen radicals.
Insights
Streptozotocin (STZ) causes diabetes in rats by damaging pancreatic islet microcirculation. Free oxygen radicals contribute to these microcirculatory disturbances, which can be prevented by superoxide dismutase.
Area of Science:
- Endocrinology
- Physiology
- Pathology
Background:
- Streptozotocin (STZ) is a common agent used to induce diabetes mellitus in rodent models.
- Understanding the early mechanisms of STZ-induced pancreatic damage is crucial for developing therapeutic strategies.
Purpose of the Study:
- To investigate the role of islet microcirculatory changes and free radical formation in STZ-induced diabetes in rats.
- To characterize the temporal sequence of microcirculatory events in pancreatic islets following STZ administration.
Main Methods:
- In vivo fluorescence microscopy was employed to monitor pancreatic microcirculation for 4 hours post-STZ administration.
- Measurements included vascular permeability, capillary blood flow velocity, and endothelial leukocyte adhesion in endocrine and exocrine pancreatic tissues.
- The effect of prophylactic superoxide dismutase administration was assessed.
Main Results:
- STZ administration rapidly increased vascular permeability in pancreatic islets within 1 hour.
- Islet blood flow velocity significantly decreased after 3 hours, leading to complete stasis in some rats, while exocrine pancreas remained unaffected.
- Prophylactic administration of superoxide dismutase mitigated STZ-induced microcirculatory damage.
Conclusions:
- STZ induces significant microcirculatory disturbances in rat pancreatic islets.
- These disturbances are, at least partly, mediated by free oxygen radicals.
- Targeting free radical formation may offer a protective strategy against STZ-induced islet damage.