Lysine Fluxes across the Jejunal Epithelium in Lysinuric Protein Intolerance

Cystine Fluxes Across the Isolated Jejunal Epithelium in Cystinuria: Increased Efflux Permeability at the Luminal Membrane

“…The methods used have been 478 DESJEUX ET AL. effective in localizing the site of lysine transport defects to the luminal membrane in cystinuria and the basolateral membrane in lysinuric protein membranes (22). The results confirm decreased intracellular accumulation of cystine observed previously in vitro, and indicate that this diminished accumulation is caused by increased luminal eMux permeability at the brush border membrane.…”

“…Intracellular Nu' and Cystine Concentrations. These concentrations were measured as previously described using pieces of jejunal epithelium and the immediately underlying tissue without the muscular layer (22). In brief, the tissue was shaken at 37°C for 60 min in 10 ml of Ringer containing 0.3 mM of L-cystine, 1.5 pCi of L -~~S cystine, 1 pCi of "Na, and 12.5 pCi of 3H polyethylene glycol as an extracellular marker.…”

“…The basic assumptions of the calculations (22) are: I) The system is in a steady state as indicated by constant isotopic and electrical fluxes, 2) cystine is transported through one cellular compartment, i.e. the epithelial cells, 3) intracellular cystine to cysteine metabolism does not occur (see "Discussion7'); the results are therefore expressed in 35S or 3H "cystine-equivalents," and 4) the absence of a transconcentration effect across the luminal membrane.…”

Metabolic fuel selection by intestinal epithelium

“…In vivo, malabsorption of the three amino acids, lysine, arginine and ornithine, given as free amino acids or dipetides, by the small intestine and the kidney (Smell, 1989) and plasma concentrations of dibasic amino acids are low. In vitro, entry of the amino acids across the luminal membrane of the epithelial cells is not impaired but the exit permeability across the basolateral membrane to the blood is grossly impaired (Desjeux et al 1980). In addition, the transport defect is also found in other plasma membranes (fibroblast, hepatocyte).…”

Renal transport of lysine and arginine in cystinuria.

“…Kato (1977), studying in vivo renal clearance of patients with cystinuria, has postulated a transport defect of the low-concentration system of the dibasic amino acids in cystinuria. Coicadan et al (1980) have suggested a transport defect of lysine in the luminal membrane of the intestinal brush border cell in cystinuria, and Desjeux et al (1980) and Rajantie et al (1980Rajantie et al ( , 1981 have demonstrated a transport defect of the dibasic amino acids in the basolateral membrane of both the gut mucosa and renal tubule in LPI, indicating the location of the defective transport site by the cell membrane. In the present experiments, in vivo renal transport of lysine and arginine in patients with cystinuria was examined to study the defective transport mechanism of the tubular cell of this disease.…”