Figure 11.

Immunolabeling of cathepsins L and B in mature granules of mouse islet β-cells. (A and B) Ultrathin cryosections were immunolabeled for cathepsin L (10-nm gold) and insulin (15-nm gold), demonstrating the presence of cathepsin L labeling in mature β-granules. In B, two exocytotic profiles at the plasma membrane (P) are seen. (C) Triple labeling for insulin (5-nm gold), cathepsin L, (10-nm gold), and cathepsin B (15-nm gold) demonstrates a mature granule immunopositive for cathepsin L and immunonegative for cathepsin B (arrow). Occasional immunogold labeling of cathepsin B is indicated by arrowheads. Bars, 200 nm.