Immunohistochemical localization of adropin in the small intestine of rats

The aim of this study was to determine the occurrence and distribution of adropin in the small intestine in control and gastrectomized rats. The study was carried out on 12 Wistar rats. Six control rats (SHO) underwent a sham operation. Six rats were subjected to gastrectomy (Gx); i.e. resection of the antrum and the glandular part of the stomach. Six weeks after the surgery, the rats were sacrificed. The duodenum and middle part of the jejunum were collected for immunohistochemical and immunofluorescence procedures. An immunopositive reaction to ADR was detected in the duodenum and jejunum, in crypts, and in enterocytes located along the entire length of the villi. Furthermore, more intense ADR immunoreactivity was observed in the crypts and villi of the duodenum than in the jejunum. The presence of adropin was also detected in the submucosa and muscularis externa of the duodenum and jejunum, in the cells of Brunner's gland of the duodenum, and in myenteric and submucosal plexus nerve. The ADR immunoreactivity in the crypts and villi in the duodenum and jejunum was lower in the Gx rats compared to the SHO rats. The ADR distribution in the duodenum and jejunum has also been confirmed in immunofluorescence studies. In conclusion, our data demonstrated ADR expression in all histological layers of the small intestine in the rats. Gx reduced ADR immunoreactivity in the crypts and enterocytes. This may suggest a potential impact of ADR on intestine function such as absorbability and immune reactions. However, further research is needed to explain the ADR role in gastrointestinal functions.