Imaging Cyclic AMP Changes in Pancreatic Islets of Transgenic Reporter Mice
Figure 3
Pancreatic islets function normally in double transgenic Ins2-rtTA/pBI-cAMP mice induced to express the cAMP reporter in pancreatic islet β-cells.
A. Cryosections of a pancreas, immunostained with anti-insulin to reveal islets of Langerhans (red) and anti-GFP (green). The overlay (right) shows that only β-cells express the transgenic cAMP reporter. We detected no gross changes in islet histology in transgenic mice. B. Reporter expression does not interfere with glucose homeostasis. Double transgenic mice, subjected to a Glucose Tolerance Test before (○), and 1 week after (•) induction of the cAMP reporter showed similar rise and fall in plasma glucose (mean±s.e.m.; n = 5 mice). C. β-cells from Ins2-rtTA/pBI-cAMP mice show normal glucose-stimulated Δ[Ca2+]i (imaged with Fura-2). Glucose was elevated from 3 mM (basal) to 11 mM (grey bar, 11G). Intracellular [Ca2+] decreased transiently (arrow), then rapidly increased with a series of oscillations that continued for several minutes after glucose returned to the basal concentration. Similar responses were obtained in islets from wild-type mice (not shown).