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Ammonium transport in the intestine chronically exposed to urine: is it reduced over time?
1Department of Urology, Massachusetts General Hospital and Harvard Medical School, Boston 02114, USA.
Objectives:
To determine whether chronic exposure of urine to intestinal segments alters ammonium transport and thereby would be expected to reduce the metabolic acidosis of intestinal diversion.
Methods:
Ileal patch cystoplasty specimens and control-matched ileum segments were harvested from mongrel dogs after 6 months. Acridine orange fluorescence quenching was used to determine the Km, Vmax, and Hill coefficient of ileal patch cystoplasty membrane vesicles and of control-matched ileum membrane vesicles. Enzyme activities for glucose uptake and sodium transport were also determined.
Results:
A shift of the Km and Vmax for ammonium occurred with chronic exposure of the intestine to urine. However, some specific enzyme activities remained unchanged, particularly those of intracellular and basolateral membrane locations.
Conclusions:
Chronic exposure of the intestine to urine alters transport at the brush border by reducing the number of ports available for ammonium transport. It is less detrimental to intracellular and basolateral membrane enzyme activities.