Desjeux J F, Vonlanthen M, Dumontier A M, Simell O, Legrain M
Pediatr Res. 1987 May;21(5):477-81. doi: 10.1203/00006450-198705000-00011.
In cystinuria, renal clearance of cystine frequently exceeds creatinine clearance, suggesting net cystine secretion; and absorption of the (di)basic amino acid is impaired at the luminal membrane of the jejunal and probably also renal tubular epithelium. We studied cystine transport in vitro in jejunal biopsy specimens of eight subjects with homozygous cystinuria and in 12 controls. Cellular/medium cystine distribution ratio was reduced in cystinuria (1.36 +/- 0.36 versus 5.36 +/- 0.61, p less than 0.001). Cystine influx across the luminal membrane was normal (221 +/- 48 versus 261 +/- 79 pmol X h-1 cm-2). Measurement of transepithelial cystine fluxes showed net absorption in controls but secretion in cystinuria. Apparent permeability coefficients were close to normal in cystinuria except that the efflux permeability at the luminal membrane was significantly increased (0.839 +/- 0.22 versus 0.186 +/- 0.12 X h-1 cm-2), and, accordingly, at the luminal membrane, the influx over efflux permeability ratio was small (1.01 +/- 0.50 versus 4.95 +/- 0.80, p less than 0.001). The defect in cystine transport in cystinuria is apparently not caused by decreased influx but increased efflux of cystine (or cystine) from the cell to the lumen across the luminal membrane.
在胱氨酸尿症中，胱氨酸的肾脏清除率常常超过肌酐清除率，提示存在净胱氨酸分泌；并且（二）碱性氨基酸在空肠腔面膜以及可能在肾小管上皮的吸收受损。我们对8名纯合子胱氨酸尿症患者和12名对照者的空肠活检标本进行了体外胱氨酸转运研究。胱氨酸尿症患者的细胞/培养基胱氨酸分布比率降低（1.36±0.36对5.36±0.61，p<0.001）。跨腔面膜的胱氨酸流入正常（221±48对261±79 pmol·h-1·cm-2）。跨上皮胱氨酸通量的测量显示，对照组为净吸收，而胱氨酸尿症患者为分泌。胱氨酸尿症患者的表观渗透系数接近正常，但腔面膜的流出渗透率显著增加（0.839±0.22对0.186±0.12·h-1·cm-2），因此，在腔面膜处，流入与流出渗透率之比很小（1.01±0.50对4.95±0.80，p<0.001）。胱氨酸尿症中胱氨酸转运的缺陷显然不是由胱氨酸流入减少引起的，而是由胱氨酸（或胱氨酸）从细胞经腔面膜向管腔的流出增加所致。
