A histological method for the visualization of the intercellular permeability barrier in mammalian stratified squamous epithelia

Abstract

Mammalian epidermis and oral epithelial possess an intercellular permeability barrier which is located in the superficial region of the tissue. This study reports a staining reaction which appears to demonstrate a histological correlate of this functional property. Specimens of ear skin, palate, buccal and oesophageal mucosa and of cornea and bladder were obtained from adult rabbits and rats, bisected and either incubated in vitro with 2.5% horseradish peroxidase as a tracer or fixed and processed for light microscopy and stained with a modification of Hart's elastin stain. Examination of specimens prepared by each procedure showed a complementary staining pattern in the intercellular spaces of the stratum corneum or in the superficial region of the non-keratinized tissue. In the epidermis and oral and oesophageal epithelia, the region which excluded the tracer stained with the modified elastin stain. In contrast, the corneal and bladder epithelia neither excluded the tracer nor showed intercellular staining. This relationship between staining of the intercellular space and the exclusion of tracer suggests that the intercellular material in the superficial region of epithelia may be chemically altered to form a barrier substance, possibly as the result of the discharge of the contents of the membrane-coating granules which are present in all the epithelia examined except the cornea and bladder.

Evaluation of pig esophageal mucosa as a permeability barrier model for buccal tissue

“…MCG have also been found in esophageal epithelium 12. Their appearance and localization is similar to that in the buccal mucosa and the secreted material has been correlated to the performance of the permeability barrier 13,14…”

“…Similarly, they first appear in the prickle‐cell layer and they subsequently fuse with the plasma membrane and secrete their content in the intercellular space. This intercellular material is related to the permeability barrier: the penetration of horseradish peroxidase across rabbit buccal and esophageal epithelium was blocked at the level of MCG secretion 13,22. That having been said, the composition of the esophageal intercellular material is not well‐known, although glycoconjugates similar to those in the buccal mucosa have been found 21.…”

Uptake of Horseradish Peroxidase (HRP) by the Urinary Bladder Epithelial Cells of Several Mammalian Species

“…Hill et al (1982) also observed the uptake of HRP by rabbit bladder epithelium. They treated small pieces of dissected bladder tissue (1-2 mm cubes) with HRP, but they did not describe the precise distribution of HRP within the epithelium.…”