Proceedings of The Physiological Society

Europhysiology 2018 (London, UK) (2018) Proc Physiol Soc 41, PCA097

Poster Communications

Expression of aquaglyceroporins in the bovine gastrointestinal tract

C. Zhong1, G. Stewart1

1. School of Biology and Environmental Science, University College Dublin, Dublin, Ireland.

Urea nitrogen salvaging (UNS) is a crucial mechanism that ruminants evolved to conserve nitrogen. Facilitative UT-B urea transporters have been proven to be involved in urea transport across rumen epithelial layers and thus efficiently facilitate the UNS process. Recently, functional studies showed that apart from UT-B, aquaporins (AQPs) - probably aquaglyceroporins (AQGPs, i.e. AQP3, AQP7, AQP9 and AQP10) - were also involved in urea transport across rumen. This current study aims to investigate how these AQGPs are expressed in bovine gastrointestinal (GI) tract, especially in rumen, and hence provide evidence of for their physiological roles in UNS. Initial end-point RT-PCR analysis suggested that except for AQP10, all these AQGPs genes were transcribed along ruminant GI tract but with varying abundance specific for genes and locations. In dorsal and ventral sacs of rumen, AQP3 was the most abundant transcript, followed by weak AQP7 expression and very weak AQP9 expression. In the lower GI tract, each gene, especially for AQP7 and AQP9, displayed a decreasing expression pattern downward the GI tract: abomasum > jejunum > colon. Using immunoblotting, AQP3 protein was detected in rumen, with a 45 kDa glycosylated form and a 25 kDa core unglycosylated protein. Further immunolocalization studies showed that like UT-B, AQP3 also mainly located at cell membranes of stratum basale layer but seemed to have a lower abundance. In conclusion, this study describes the transcripts expression patterns of AQP3, AQP7, AQP9 and AQP10 along ruminant GI tract, confirmes that glycosylated AQP3 protein is present in rumen and characterizes, for the first time, the precise cellular location of AQP3 transporters in the bovine rumen epithelium.

Where applicable, experiments conform with Society ethical requirements