Expression and Localization of Aquaporin 4 and Aquaporin 5 along the Large Intestine of Colostrum-Suckling Buffalo Calves

Abstract

Aquaporins (AQPs) are membrane channel proteins that play a role in regulating water permeability in many tissues. To date, seven isoforms of AQPs have been reported in the gastrointestinal tract in different mammalian species. In contrast, both tissue distribution and expression of AQPs are unknown in the buffalo. The purpose of this study was to investigate the expression of both AQP4 and AQP5 mRNAs and their relative proteins in the large intestinal tracts of buffalo calves after colostrum suckling using reverse transcriptase polymerase chain reaction (RT-PCR), Western blotting and immunohistochemistry. Our results revealed a diversified tissue AQP4 and AQP5 immunolocalization accompanied by their highest expression in the tissues of colostrum-suckling buffalo calves confirmed by Western blotting. In particular, AQP4 was distributed along the endothelium and enterocytes while AQP5 in the endocrine cells. These findings provide direct evidence for AQP4 and AQP5 expression in the large intestine, suggesting that different AQPs collaborate functionally and distinctively in water handling during intestinal development, especially during the first period after delivery.

Aquaporins in Health and Disease: An Overview Focusing on the Gut of Different Species

“…In addition, in our previous study conducted on buffalo calves fed with colostrum for one week, a different pattern of AQP1, 4, and 5 expression was observed with respect to the control group fed milk. These data indicate that a specific regulation of AQP function and distribution could be achieved according to the nutritional level or the food preference [77,78,79]. …”

“…AQP4-IR was localized on the basolateral membrane of epithelial cells isolated from the rat, buffalo, and porcine colon [53,79,111,119]. In addition, AQP4 expression was found in the endothelium and enteric neurons of the buffalo and rodent colon [79,119].…”

“…In addition, AQP4 expression was found in the endothelium and enteric neurons of the buffalo and rodent colon [79,119]. This localization suggests the involvement of the enteric nervous system in body fluid homeostasis by monitoring changes in osmotic pressure and controlling water movement across the mucosa.…”

“…This localization suggests the involvement of the enteric nervous system in body fluid homeostasis by monitoring changes in osmotic pressure and controlling water movement across the mucosa. The AQP4 protein and relative mRNA were also revealed in the buffalo and rat large intestine [79,109]. …”

“…AQP5-IR, protein, and relative mRNA were shown in the endocrine cells of the buffalo large intestine [79] while AQP7-IR was distributed in the surface epithelial cells of the crypt of the rat colon and cecum [54,109]. …”