Figure 2. Distribution of insulin granules in exophilin-8-null β-cells.
(A) Islets isolated from WT and exophilin8-KO mice were coimmunostained with anti-insulin and anti-Na+-K+ ATPase antibodies. Note that the antibodies were accessible to only surface β-cells. Bars, 10 μm. Insets show details at a higher magnification. (B) The isolated islets were cultured overnight and incubated in 2.8 mM glucose buffer at 37°C for 1 hr. They were then fixed and processed in a standard fashion for electron microscopy. Bar, 1 μm. Squares in left panels are shown at a higher magnification in right panels. Black arrowheads indicate the position of the plasma membrane, whereas red arrows indicate granules directly attached to the plasma membrane. (C) The distributions of insulin granules were morphometrically analyzed by electron microscopy in a total of nine β cells from three, 20- to 22-week-old male WT (gray columns) or KO (red columns) mice (three cells from each individual mouse). All granules with centers that resided within 500 nm of the plasma membrane were categorized at 100 nm intervals. Data are shown as a percentage of the total granule number, and are shown as means ± SEM. *p values calculated using two-tailed unpaired t-test are 0.00182 (<100 nm), 0.01360 (100–200 nm), 0.021 (200–300 nm), and 1.4 × 10−3 (≥500 nm), respectively.