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Cadmium uptake through the anion exchanger in human red blood cells.
Author(s) -
Lou M,
Garay R,
Alda J O
Publication year - 1991
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1991.sp018826
Subject(s) - dids , bicarbonate , chemistry , cadmium , amiloride , ouabain , ion exchange , nuclear chemistry , biochemistry , inorganic chemistry , medicinal chemistry , membrane , ion , sodium , organic chemistry
1. The initial rate of Cd2+ uptake in human red cells was measured by atomic absorption spectrophotometry. 2. About 96% of Cd2+ uptake was inhibited by DIDS (4,4'‐diisothiocyanatostilbene‐2,2'‐disulphonic acid) with IC50 (concentration giving 50% of maximal inhibition) of 0.3 microM and by furosemide with IC50 of 500 microM and was resistant to ouabain and amiloride. This indicates the implication of the [Cl(‐)‐HCO3‐] anion exchanger in Cd2+ uptake. 3. DIDS‐sensitive Cd2+ uptake required the presence of external HCO3‐. HCO3‐ ions had a biphasic effect on Cd2+ uptake. Low bicarbonate concentrations were stimulatory, suggesting formation of translocating bicarbonate‐cadmium complexes. Higher bicarbonate concentrations were inhibitory, suggesting further bicarbonate complexation with formation of non‐translocating species. Depending on the presence or absence of external Cl‐, a maximal Cd2+ uptake of 1.7 or 0.37 mmol (l cells)‐1 h‐1 was observed at bicarbonate concentrations of 15.6 or 11 mM respectively. 4. In the presence of bicarbonate, external Cl‐ ions strongly stimulated Cd2+ uptake, with linear increase between 70 and 125 mM. This suggests that one translocating species may have chloride as ligand. 5. DIDS‐sensitive Cd2+ uptake was modestly inhibited by physiological concentrations of external phosphate and was resistant to external K+, Mg2+ and Ca2+. 6. In conclusion, the anion exchanger is the major transport mechanism for red cell cadmium uptake. Translocating species appear to be monovalent anion complexes of cadmium with HCO3‐ such as [Cd(OH)(HCO3)2]‐ and [Cd(OH)(HCO3)Cl]‐.