The vital role of melatonin in the intestinal mucosal barrier integrity in chick.

Background: The intestinal tract, as the main place for nutrient digestion and absorption, is closely related to the health of livestock and poultry. Melatonin secreted by the pineal gland acts as an endocrine transport signaling molecule to regulate intestinal function. However, the effect on intestinal function after pineal removal is unclear.

Methods: We raised 24 chicks under 400-700 nm white light with or without pinealectomy for 21 days. We used electron microscopy, HE staining, PAS staining, immunohistochemistry, immunofluorescence staining and western blot to detect intestinal physical and to explore the effect of melatonin secreted by the pineal gland on the intestinal mucosa barrier function.

Results: The results showed that after pineal gland removal, the structure of the intestinal villi is severely damaged. Moreover, there was an obviously down-regulation in the villi length, the number of goblet cells and and its secretion of MUC2 protein, the expression level of tight junction proteins (Occludin and ZO-1) and lysozyme secreted by paneth cells, number of PCNA positive cells and macrophage, and an up-regualtion in crypt depth and apoptosis level after pinealectomy, suggesting pinealectomy-mediated melatonin level decrease damaged the intestinal physical, chemical and immune barriers.

Conclusion: Our findings provide new theoretical support for the future use of melatonin in intestinal development and new ideas about the relationship between endocrine hormone and intestinal physiology.