AJP - Renal Physiology, Vol 265, Issue 6 839-F844, Copyright © 1993 by American Physiological Society
Cystine loading induces Fanconi's syndrome in rats: in vivo and vesicle studies
A. Ben-Nun, N. Bashan, R. Potashnik, R. Cohen-Luria and A. Moran
Department of Physiology, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
To better understand the link between lysosomal cystine accumulation and
the renal impairment seen in cystinosis, we have studied the effect of
cystine loading in vivo, on renal function of rats, and in brush-border
membrane vesicles (BBMV) prepared from the kidney cortex of the treated
rats. Intraperitoneal injection of cystine dimethyl ester (CDME) (400
mumol, twice a day, for 5 days) led to an increased urine volume and
excretion of glucose, phosphate, and protein. Kinetic analysis of
alpha-methylglucoside initial flux in BBMV showed reduction in maximal
transport capacity (Vmax, from 10.1 +/- 1.3 to 8.5 +/- 0.7 nmol.min-1.mg
protein-1; P < 0.01) with no change in Michaelis constant (Km, 4.80 +/-
0.08 and 4.90 +/- 0.05 mM). The number of phlorizin binding sites declined
(from 6.5 +/- 0.7 to 4.1 +/- 0.4 pmol/mg protein; P < 0.01) with no
significant change in the affinity for phlorizin (0.64 +/- 0.08 and 0.59
+/- 0.06 microM). In the cortex homogenate, cystine concentration, which
was undetectable in controls, increased to 0.97 +/- 0.09 nmol 1/2
cystine/mg protein. Two hours after CDME administration, ATP content
declined to approximately 50% of control values. This decline was
transient, and ATP content was recovered to control values 5 h after CDME
administration. The treatment did not affect ouabain-sensitive
adenosinetriphosphatase activity (40.0 +/- 3.9 and 38.6 +/- 4.7 nmol Pi.mg
protein-1.min-1) or the number and affinity of ouabain binding sites (Bmax
= 1.48 +/- 0.25 and 1.44 +/- 0.18 pmol/mg, and Kd = 0.68 +/- 0.09 and 0.72
+/- 0.12 microM, respectively). (ABSTRACT TRUNCATED AT 250 WORDS)
