Figure 2 .
Effect of chronic stress on horseradish peroxidase (HRP) transport and epithelial mitochondria. Mast cell deficient rats (Ws/Ws; left) and their normal mast cell containing littermates (+/+; right) were submitted to water avoidance stress (top photomicrographs) or to sham stress (bottom photomicrographs) for five consecutive days. (A) Photomicrograph showing an HRP filled endosome (large arrowhead) in a colonocyte of a stressed Ws/Ws rat. Paracellular passage of HRP and mitochondrial abnormalities were not observed in Ws/Ws rats. (B) Larger and more numerous HRP filled endosomes (arrowheads) as well as HRP within tight junctions and paracellular spaces between colonocytes (arrows) were observed in the colon of stressed +/+ rats, as shown in this photomicrograph. Epithelial damage is demonstrated by swollen mitochondria with loss of cristae. (C, D) Colonocytes with small endosomal uptake of HRP (arrowheads) and normal mitochondria from sham stressed Ws/Ws (C) and +/+ rats (D), respectively. Mitochondrial surface area was significantly increased in stressed +/+ rats compared with the three other groups (table 1). Magnification: ×3000. Each photomicrograph is representative of four rats/group and 15 sections/colonic tissue.