Isolation and culture of murine islets
The isolation of murine islets was described in our previous study (Hanet al. , 2001). Briefly, the pancreas was digested with collagenase (Sigma, 1 mg/mL) via common bile duct injection. The digest was then washed and fractionated by gradient centrifugation in Histopaque (Sigma). The islets were viewed with a stereomicroscope and picked up with a pipette. Isolated islets were cultured in RPMI 1640 with 10% FBS in an incubator of 5% CO2 at 37°C overnight.