Ammonium transport in the intestine chronically exposed to urine: Is it reduced over time?

Objectives. To determine whether chronic exposure of urine to intestinal se gments alters ammonium transport and thereby would be expected to reduce th e metabolic acidosis of intestinal diversion. Methods. Ileal patch cystoplasty specimens and control-matched ileum segmen ts were harvested from mongrel dogs after 6 months. Acridine orange fluores cence quenching was used to determine the Km, Vmax, and Hill coefficient of ileal patch cystoplasty membrane vesicles and of control-matched ileum mem brane vesicles. Enzyme activities for glucose uptake and sodium transport w ere also determined. Results. A shift of the Km and Vmax for ammonium occurred with chronic expo sure of the intestine to urine. However, some specific enzyme activities re mained unchanged, particularly those of intracellular and basolateral membr ane locations. Conclusions. Chronic exposure of the intestine to urine alters transport at the brush border by reducing the number of ports available for ammonium tr ansport. It is less detrimental to intracellular and basolateral membrane e nzyme activities. (C) 1999, Elsevier Science Inc.