pH-dependent transport of cadmium in rat renal brush border membrane vesicles:: cadmium efflux via H+-antiport

被引:10
作者
Endo, T
Kimura, O
Sakata, M
机构
[1] Hlth Sci Univ Hokkaido, Fac Pharmaceut Sci, Ishikari, Hokkaido 06102, Japan
[2] Asahikawa Kousei Hosp, Asahikawa, Hokkaido 078, Japan
关键词
cadmium; secretion; efflux; pH; renal brush border membrane vesicles; H+-antiport system;
D O I
10.1016/S0378-4274(98)00139-8
中图分类号
R99 [毒物学(毒理学)];
学科分类号
100405 ;
摘要
The effects of pH on the Cd efflux across the renal brush border membrane were investigated using isolated rat renal brush border membrane vesicles (BBMV). BBMV equilibrated at pH 5.5 or 7.5 (pH(in)) were mixed with an experimental buffer at pH 5.5 or 7.5 (pH(out)) containing CdCl2. After the incubation with CdCl2, BBMV were washed with a chelating agent, EGTA, to remove Cd bound to the outer surface of BBMV. The initial accumulation of Cd in BBMV incubated for 1, 3 or 5 min at pH(in) = 5.5 and pH(out) = 7.5 (outwardly directed H+-gradient) was significantly higher than that at pH(in) = pH(out) = 7.5, but the equilibrated Cd accumulation incubated for over 15 min was almost the same. FCCP, a protonophore, diminished the increasing effect of the H+-gradient on the initial Cd accumulation, whereas valinomycine, a K+ ionophore, did not. Kinetic analysis of the Cd accumulation incubated with different concentrations of CdCl2 suggests that Cd is taken up into BBMV via the unsaturable component and saturable component and the outwardly directed H+-gradient increases the V-max value of the saturable component. The BBMV were incubated with CdCl2 at different temperatures under the outwardly directed H+-gradient, and the increase in Cd accumulation due to the gradient was analyzed by an Arrhenius plot. The plot of increased Cd accumulation was nonlinear, suggesting the involvement of a carrier-mediated process. These findings suggest that the outwardly directed H+-gradient increases the Cd efflux across the renal brush border membrane via H+-antiport system. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.
引用
收藏
页码:99 / 107
页数:9
相关论文
共 25 条
[1]  
BRADFORD MM, 1976, ANAL BIOCHEM, V72, P248, DOI 10.1016/0003-2697(76)90527-3
[2]   TEMPERATURE-DEPENDENCE OF SOLUTE TRANSPORT AND ENZYME-ACTIVITIES IN HOG RENAL BRUSH-BORDER MEMBRANE-VESICLES [J].
DESMEDT, H ;
KINNE, R .
BIOCHIMICA ET BIOPHYSICA ACTA, 1981, 648 (02) :247-253
[3]   DISCREPANCY BETWEEN THE NEPHROTOXIC POTENCIES OF CADMIUM-METALLOTHIONEIN AND CADMIUM CHLORIDE AND THE RENAL CONCENTRATION OF CADMIUM IN THE PROXIMAL CONVOLUTED TUBULES [J].
DORIAN, C ;
GATTONE, VH ;
KLAASSEN, CD .
TOXICOLOGY AND APPLIED PHARMACOLOGY, 1995, 130 (01) :161-168
[4]  
Endo T, 1996, BIOL PHARM BULL, V19, P944
[5]   Cadmium uptake from apical membrane of LLC-PK1 cells via inorganic anion exchanger [J].
Endo, T ;
Kimura, O ;
Sakata, M .
PHARMACOLOGY & TOXICOLOGY, 1998, 82 (05) :230-235
[6]   Comparative studies of cadmium and mercury accumulation by LLC-PK1 cells: Effects of pH on uptake and efflux [J].
Endo, T ;
Kimura, O ;
Sakata, M .
TOXICOLOGY LETTERS, 1996, 87 (2-3) :77-83
[7]   Effects of zinc and copper on cadmium uptake by brush border membrane vesicles [J].
Endo, T ;
Kimura, O ;
Hatakeyama, M ;
Takada, M ;
Sakata, M .
TOXICOLOGY LETTERS, 1997, 91 (02) :111-120
[8]   PROPERTIES OF BRUSH-BORDER VESICLES ISOLATED FROM RAT-KIDNEY CORTEX BY CALCIUM PRECIPITATION [J].
EVERS, C ;
HAASE, W ;
MURER, H ;
KINNE, R .
MEMBRANE BIOCHEMISTRY, 1978, 1 (3-4) :203-219
[9]  
FRIBERG L, 1984, ENVIRON HEALTH PERSP, V54, P1
[10]  
HIRANO T, 1995, BIOL PHARM BULL, V18, P342