Decreased uptake of L-cystine by duodenal brush border membrane vesicles from patients with cystinuria.
BACKGROUND
The pathophysiology of cystinuria remains unclear. Decreased absorption of L-cystine across brush border membranes of small intestinal and renal proximal tubular epithelial cells is likely but has not been directly demonstrated.


OBJECTIVE
To compare the rates of L-cystine transport by isolated duodenal brush border membranes of normal individuals and patients with cystinuria.


METHODS
Distal duodenal biopsies were taken from normal individuals and patients with cystinuria. Brush border membrane vesicles (BBMV) were prepared using magnesium aggregation and differential centrifugation and the rates of L-cystine transport into the vesicles measured using a rapid filtration technique.


RESULTS
Rates of L-cystine transport by BBMV from patients with cystinuria were reduced at 5 minute (p = 0.003) and 30 minute (p = 0.053). Time points, indicating that L-cystine absorption across brush border membranes is abnormal in cystinuria.
Furlong
T J
TJ
Department of Medicine, Royal North Shore Hospital, St Leonards, NSW.
Stiel
D
D
D000328:Adult; D001693:Biological Transport, Active / Q000502:physiology; D003553:Cystine / Q000378:metabolism*; D003555:Cystinuria / Q000378:metabolism*; D004386:Duodenum / Q000378:metabolism*; D005260:Female; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism; D008297:Male; D008871:Microvilli / Q000378:metabolism
D003553:Cystine