The uptake of horseradish peroxidase and its subsequent redistribution by guinea pig gallbladder in vivo.

Horseradish peroxidase (HRP) was injected into the emptied gallbladder of guinea pigs at laparotomy. The fate of the HRP was observed by light and electron microscopy over the following 2 hr. Within 5 min. HRP appeared in pits and apical vesicles either as a rim of increased electron density or more evenly distributed throughout the pit or vesicle. The pits and vesicles were more frequently seen at the edge of the cell apex. From 15 min. HRP was identified in the basolateral cell space in increasing quantities with spill over through the basement membrane into the lamina propria: by 30 min. and 2 hr, little further change was observed. The quantity of nonspecific electron density in epithelial cell multivesicular bodies and residual bodies made the assessment of intracellular handling of the HRP impossible. Dilution of the HRP in the lamina propria made the identification of the eventual fate of the HRP difficult to determine.