Effect of calpain 8 or 9 deficiency on mucous granule formation and secretion.

(A) Electron micrographs of the pit cells of WT, Capn8−/−, and Capn9−/− mice before (a–c) and after (d–f) ethanol administration. The gastric lumen is at the top of each photograph. MG, mucous granule; N, nuclei. Bars, 2 µm. (B) Comparison of the number of mucous granules per pit cell for WT, Capn8−/−, and Capn9−/− mice before (white bars) and after (black bars) ethanol administration. Top-pit (fully differentiated) cells randomly selected from stomach samples were analyzed for each experimental group (n = 45, 41, and 44 for the WT, Capn8−/−, and Capn9−/− mouse stomach groups before ethanol administration, and n = 36, 41, and 42 for those groups after the administration, respectively). The sum of the mucous granules divided by the number of cells analyzed was defined as the average number of granules per cell. Each mean value was standardized to that for the WT group before ethanol administration, which was defined as 100%. Values are means ± SEM. (C) Immunostaining of WT, Capn8−/−, and Capn9−/− mouse stomachs before (a–c) and after (d–f) ethanol administration using an antibody for Muc5AC (green). Bars, 50 µm.