Cystinuria|[colon]| absence of lysine permeability in the brush border membrane of intestinal cells

摘要

The mechanism of impaired transport of cystine and dibasic amino acids in the jejunum and the kidney of cystinuric patients is poorly understood. Na-dependent L-lysine intestinal transport has been assessed, in vitro, by measurement of intracellular accumulation and of unidirectional influx across the brush border membrane in per ora biopsies performed for diagnostic purpose on 27 "control" children and 2 cystinuric patients, in the presence of 3 mM lysine in the incubation solution. The project was accepted by the Committee on Ethics of the Department of Pediatrics of the University Paris VII. In cystinuria 1) the Na-dependent lysine intracellular accumulation is abolished, 2) the Na-independent accumulation persists (the accumulation ratio is 1.69 ± 0.34) , 3) the lysine influx in μmo1/h cm2 at the luminal membrane is hardly measurable both in the presence (0.17 ± 0.03) and in the absence of Na (0.22 ± 0.09). Control values : 0.95 ± 0.14 in the presence of Na and 0.57 ± 0.08 in the absence of Na. These results suggest a specific loss of the Na-dependent L-lysine transport at the luminal membrane of the enterocytes of the intestine in the 2 patients with cystinuria. The lysine permeability at the baso-lateral membrane is probably present.