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Direct effect of lipopolysaccharide and histamine on permeability barrier of rumen epithelium.

D. P. Bu



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Direct effect of lipopolysaccharide and histamine on permeability barrier of rumen epithelium.
S. T. Gao, L. Ma, A. L. T. Zhu La, W. H. Liu, D. P. Bu*. State Key Laboratory of Animal Nutrition, Institute of Animal Science, Chinese Academy of Agricultural Sciences Beijing, China.

Disruption of rumen epithelium (RE) barrier is very common during subacute ruminal acidosis (SARA) with lipopolysaccharide (LPS) and histamine (HIS) increased in the rumen. However, the individual roles of LPS and HIS in the process of RE barriers disruption are not clear. The objective of the present investigation was to evaluate the direct effect of LPS and HIS on barrier function of RE using the Ussing chamber system. Rumen tissues (n = 8) obtained from slaughtered feedlot steers were tested for changes in permeability to fluorescein 5(6)-isothiocyanate (FITC) with LPS (1 mg/mL) and HIS (20 mmol/mL). The FITC was added at 8 mL (final concentration: 0.2 mmol/mL) in the mucosal side of the Ussing chambers to detect changes in permeability of RE, and 8 samples were collected at 20, 40, 60, and 80 min from the serosal side (2 samples in each time, one for FITC detection, the other one for LPS and HIS detection). At the end of the experiment, the tissues mounted in the chambers were collected and separated into 2 parts, one for morphological analysis and the other one for detections of mRNA abundance related to tight junction. The transepithelial short-circuit current (Isc) and tissue conductance (Gt) were recorded continuously. The data were subjected to statistical analysis using MIXED PROC in SAS 9.4, with time, treatment, and the interaction between treatment and time as fixed effects and period as repeated effect. Compared with CON, HIS increased the Isc (88.2%, P < 0.05), Gt (29.7%, P < 0.1#), and the permeability to FITC (1.23-fold, P < 0.05) of RE. The apparent permeability of LPS was 2.8-fold higher than HIS (P < 0.01). The structures of the stratum granulosum, the stratum spinosum, and the stratum basale of histamine treated RE were severely damaged. The mRNA abundance of OCLN in RE was decreased by HIS (2.13-fold, P < 0.05). As such, the results of the present study suggested a direct role of HIS in the processing of the disruption of RE barrier function even without the cooperation of acidification.

Keywords: lipopolysaccharide, histamine, barrier function.