Effects of Combined or Along VFA, pH, Lipopolysaccharide and Histamine on the Rumen Epithelial Permeability of Dairy Goats In Vitro

This study investigated whether concurrent presence of lipopolysaccharide (LPS) and histamine (HIS) have the potential to increase permeability of the ruminal epithelium at physiological pH and acidotic ruminal pH. Nine 2.5-year-old female lactating Saanen dairy goats (42.79 ± 5.61 kg of BW; Mean ± SD) were used as a ruminant model. ruminal epithelium of goats were collected and mounted in Ussing chambers on their mucosal side in different gradient buffer solutions (pH 7.4, 5.5 and 5.2) containing LPS (0, 30 and 60 KEU·mL-1) or HIS (0, 0.5 and 10 ng·mL-1). The rumen epithelial electrophysiological indexes, such as short-circuit (Isc), tissue conductance (Gt) and the permeability of marker molecules of different sizes (horseradish peroxidase, HRP and fluorescein 5(6)-isothiocyanate, FITC) from the mucosal to the serosal side, were measured. Both Isc and Gt were increased, accompanied by enhanced flux of FITC, with a decrease of mucosal pH (P < 0.05). The addition of LPS at mucosal pH 5.2 significantly increased Isc, Gt and FITC flux rates and decreased potential difference (PD) (P < 0.05). Additionally, the concurrent presence of LPS and HIS at both physiological and acidotic ruminal pH also significantly increased the permeability of ruminal epithelium asevidenced by increasing Isc, Gt and FITC flux rates and decreasing PD. In summary, our results have shown that concurrent presence of LPS 60 KEU‧mL-1 and HIS 10 ng‧mL-1 at mucosal pH 5.5 can increase the permeability of ruminal epithelium. The combination of low pH and both high LPS and HIS may increase vulnerability to aggravated rumen epithelial barrier dysfunction. © 2021 Friends Science Publishers