A low-oxygenated subpopulation of pancreatic islets constitutes a functional reserve of endocrine cells. Diabetes 2011;60: 2068–2075

OBJECTIVE—The blood perfusion of pancreatic islets is highly variable and tightly regulated by the blood glucose concentration. Thus, oxygen levels are considered crucial for islet metabolism and function. Although islet oxygenation has been extensively studied in vitro, little is known about it in vivo. The current study aimed to investigate the oxygenation of the endocrine pancreas in vivo. RESEARCH DESIGN AND METHODS—The reductive metab-olism of 2-nitroimidazoles, such as pimonidazole, has previously been extensively used in studies of oxygen metabolism both in vitro and in vivo. At tissue oxygen levels,10 mmHg, pimonidazole accumulates intracellularly and may thereafter be detected by means of immunohistochemistry. Islet oxygenation was investi-gated in normal, 60 % partially pancreatectomized, as well as whole-pancreas–transplanted rats. Moreover, leucine-dependent protei