Ammonia is product of protein metabolism and its reabsorption occur by non-selective cation channels across rumen epithelium otherwise it will not be available as non-protein nitrogen source and excreted out causing hazard to environment. At physiological pH, ammonia is present as NH4+ in rumen and its transport leads to electrophysiological changes. It was reported that addition of menthol to the isolated rumen epithelium of cattle cause electrophysiological changes, primarily linked to the ammonium transport suggesting presence of non-selective cation channels. Addition of cation channel modulators such as menthol to diet can enhance absorption of nitrogen in the rumen. Scarce data was available for rumen epithelium of goats which has a large contribution in livestock population and has a great potential for mutton market revealing effect of cation channel modulators on electrophysiology and ammonium transport. Objective of this study was to investigate the effect of menthol on electrophysiological changes and its link to ammonia transport in the isolated rumen epithelium of goats.
Hypothesis
Menthol may affect the electrophysiology of the isolated rumen epithelium of goats and enhance ammonia transport across rumen epithelium.
Methodology
Ten goats of uniform age and weight were selected and slaughtered in a local slaughter house. Reticulorumen was removed from the abdominal cavity and cleaned in a standard transport buffer solution. Serosal layer of rumen was removed and mounted in the Ussing chamber. Rumen epithelium was incubated with transport buffer solution and after 20 minutes replaced with ammonia containing buffer solution (10mM and 40mM respectively)
46
and changes in bioelectric parameters were observed. Menthol in concentration of 1mM was added to mucosal side and electrophysiological parameters like Isc and Gt were observed. Moreover, pH of serosal side was checked after menthol treatment at time intervals 20, 60 and 90 minutes respectively to assess ammonia transport.
Results
Menthol affected the electrophysiology of isolated rumen epithelium of goats by increasing short circuit current due to increase in ammonia concentrations in the rumen. Menthol addition in 40mM NH4Cl containing solution significantly increased current (p value = 0.00). ΔIsc was also significant between the groups containing 10 and 40mM NH4Cl containing solution. Change in potential difference was significant after addition of menthol in both groups (P = 0.00). Conductance increased significantly by increasing concentration of ammonia (p value = 0.03). PH of serosal side decreased, suggesting possible NH4+ uptake, while on mucosal side increase in pH was observed.
Statistical analysis
Data were analyzed by using completely randomized ANOVA followed by post-hoc test LSD. Level of significance was set at 0.05.
Conclusion
Menthol treatment affects the electrophysiological indices of isolated rumen epithelium of goat presumably by opening non-selective cation channels and enhances ammonium transport across rumen epithelium increasing recycling of nitrogen. This may leads to efficient protein utilization by the animals.