Figure 5.

PACE-tryp^on mice displayed acinar cell necrosis and increased mortality. (A) Seven days after tamoxifen (TM) treatment, formalin-fixed pancreata were sectioned and stained with anti-high mobility group protein B1 (HMGB1) antibody. Prominent cytosolic translocation of HMGB1, a marker of necrosis, was frequently found in homozygous PACE-tryp^on mice but not controls (400×). (B) Counting cells with HMGB1 cytosolic translocation allowed quantitative analysis of necrotic cells in the pancreas of TM-treated control and homozygous PACE-tryp^on mice (7d). (C) Electron microscopy (4000×) demonstrated that control animals had no signs of acinar cell damage with normal endoplasmic reticulum and intact zymogen granules (left panel). In contrast, homozygous PACE-tryp^on mice (7d) showed abundant intercellular debris and severely damaged acinar cells leaking their content into the enlarged lumen (right panel). (D) Mortality in PACE-tryp^on mice with maximal-rapid induction with TM (TM^max) was significantly higher than those treated with gradual-repetitive induction with TM (TM^grad; control, n=15; TM^grad, n=12; TM^max, n=15; p<0.05). (E) Prominent neutrophil infiltration in the lung of homozygous PACE-tryp^on mice (7d) was identified by Gr-1 staining (200×). (F) Examination of lung tissue at a time point where mortality was expected to occur (10 days) revealed significantly elevated histomorphological scores (n=4, p<0.01).