Pancreatic islets are highly vascularized and arranged so that regions containing β-cells are distinct from those containing other cell types. While islet blood flow has been studied extensively, little is known about the dynamics of islet blood flow during hypoglycemia or hyperglycemia. To investigate changes in islet blood flow as a function of blood glucose level, we clamped blood glucose sequentially at hyperglycemic (~300 mg/dl or 16.8 mM) and hypoglycemic (~50 mg/dl or 2.8 mM) levels while simultaneously imaging intra-islet blood flow in mouse models that express GFP in the β-cells or yellow fluorescent protein (YFP) in the α-cells. Using line-scanning, confocal microscopy, in vivo blood flow was assayed after intravenous injection of fluorescent dextran or sulforhodamine-labeled red blood cells. Regardless of the sequence of hypoglycemia and hyperglycemia, islet blood flow is faster during hyperglycemia, and apparent blood volume is greater during hyperglycemia than hypoglycemia. However, there is no change in the order of perfusion of different islet endocrine cell types in hypoglycemia compared to hyperglycemia with the islet core of β-cells usually perfused first. In contrast to the results in islets, there was no significant difference in flow rate in the exocrine pancreas during hyperglycemia compared to hypoglycemia. These results indicate that glucose differentially regulates blood flow in the pancreatic islet vasculature, independent of blood flow in the rest of the pancreas.
- Copyright © 2010, American Journal of Physiology - Endocrinology and Metabolism