Mucus thickness in the gastrointestinal tract of laboratory animals.

Objectives: The objective of this study was to systematically assess the mucus thickness in the gastrointestinal tract of laboratory animals commonly used in preclinical studies.

Methods: Mucus thickness was studied post-mortem in the rat, rabbit and pig, using cryosections stained by the modified periodic acid Schiff/Alcian blue method.

Key Findings: The mucus thickness in the fundus region of the stomach was higher in the pig (190.7 ± 80.7 µm) than in the rabbit (155.1 ± 85.8 µm) and the rat (31.3 ± 11.4 µm). However, along the small intestine (ileum), mucus was thicker in the rabbit (147.8 ± 115.6 µm), followed by the pig (53.8 ± 22.1 µm) and the rat (34.1 ± 14.9 µm). This rank order was also observed in the ascending colon.

Conclusions: Inter-species variability in mucus thickness along the gut was demonstrated and suggests that the pig resembles more closely the mucus pattern of humans. This may be highly relevant when preclinical animal models are used in drug absorption studies or in the development of oral mucoadhesive drug delivery systems.