A comparative study on intestinal morphology and function of normal and injured intestines of Jian carp (Cyprinus carpio var. Jian)

This study aimed to compare the intestinal morphology, barrier function, and digestive and absorptive function of normal and injured intestines in Cyprinus carpio var. Jian. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was used for gene expression analysis, and the results were correlated with intestinal morphology and plasma biochemical parameters. The normal fish intestine was filled with chyme. Furthermore, the intestine surface was glossy and intact, and no gaps were observed in the tight junction structure (TJ). The amount of chyme in the injured intestine, however, was negligible. The wall of the injured intestine thinned and started to dissolve. Furthermore, hyperemia was observed in the injured intestine, and gaps were evident in the TJ structure of the injured intestinal mucosa. The levels of both diamine oxidase and D-lactate in the injured intestine were significantly higher than those in the normal intestine (p <.05). Protease, lipase, amylase, Na+/K+-ATPase, and alkaline phosphatase (AKP) activities in the proximal intestine of normal fish were significantly higher than that in the injured intestine of fish (p <.05). Meanwhile, Lipase, Amylase, AKP, Na+/K+-ATPase and gamma-GT mRNA levels in the proximal segment of the injured intestine were significantly lower than that in the normal intestine (p <.05). However, Claudin-3c, Claudin-7, Qccludin and ZO-1 mRNA levels showed the opposite results. Taken together, intestinal injury decreased digestive and absorptive function and disrupted the TJ barrier, which consequently increased the permeability of the intestinal mucosa.