Pancreatic fate of 6-deoxy-6-[125I]iodo-D-glucose: in vitro experiments

The apparent distribution space of 6-deoxy-6-[125I]iodo-D-glucose, recently proposed as a tracer of D-glucose transport, was measured in rat isolated islets, acinar tissue, and pieces of pancreas. While such a space reached a steady-state value corresponding to the 3HOH volume in pancreatic islets within 5 min, it slowly increased in pieces of pancreas and, even after 60-min incubation, remained lower than the 3HOH volume. Moreover, the net uptake of 6-deoxy-6-[125I]iodo-D-glucose by pancreatic pieces was inhibited by unlabeled 6-deoxy-6-iodo-D-glucose, D-glucose, and cytochalasin B, while being less or not affected by these agents in isolated islets. A preferential labeling of the endocrine, relative to exocrine, moiety of the pancreas was documented both by comparing, after 2 min incubation, the uptake of 6-deoxy-6-[125I]iodo-D-glucose by pieces of pancreas from normal vs streptozotocin-injected rats and by comparing the radioactive content of pancreatic islets and acinar tissue obtained from normal rats injected intravenously 3 min before sacrifice with 6-deoxy-6-[125I]iodo-D-glucose. It is proposed, therefore, that advantage could conceivably be taken from the vastly different time course for the uptake of selected monosaccharides by pancreatic islets vs acinar cells in the perspective of imaging of the endocrine pancreas by a non invasive method.