Ammonia-nitrogen turnover in the rabbit caecum and exchange with plasma urea-N

Continuous infusion and single-shot administration of 15NH4Cl into the caecum of the conscious rabbit was used to measure caecal ammonia flux. Continuous infusion of 15NH4Cl and sampling from both the caecal ammonia and blood urea pools indicated that 0.27 of plasma urea-nitrogen was derived from caecal ammonia-N. Values from intravenous [15N]urea and intracaecal 15NH4Cl infusions were used to produce two models of the movement of N between these two metabolic pools. Further analysis of the results suggested an alternative model involving a third pool associated with the caecal mucosa and values for this model are also presented.