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Passive transport and binding of lead by human red blood cells.
Author(s) -
Simons T J
Publication year - 1986
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.1986.sp016219
Subject(s) - dids , chemistry , adenosine triphosphate , red blood cell , cytosol , biophysics , binding site , membrane transport , ion transporter , efflux , biochemistry , phosphate , passive transport , membrane , biology , enzyme
The uptake of Pb into human red blood cells has been studied using Pb buffers. Passive Pb movements can be studied conveniently when the cells are depleted of adenosine 5'‐triphosphate (ATP), to eliminate active transport, and of inorganic phosphate, to prevent precipitation of lead phosphate. Pb can cross the membrane passively in either direction. Influx and efflux show similar properties. Passive Pb transport is strongly stimulated by HCO3‐, and is reduced by replacing Cl‐ with ClO4‐. It is inhibited by low concentrations of 4‐acetamido‐4'‐isothiocyanostilbene‐2,2'‐disulphonic acid (SITS) and 4,4'‐diisothiocyanostilbene‐2.2'‐disulphonic acid (DIDS), characteristic inhibitors of anion transport. Pb uptake is unaffected by varying the external concentrations of Na+, K+ and Ca2+. When Pb enters the cell, it binds mainly to haemoglobin. The ratio of bound Pb:free Pb2+ in the cytosol is estimated to be 6000:1. Pb binding to haemoglobin is unaffected by oxygenation. Binding to albumin is quantitatively similar to binding to haemoglobin. The implications of these results for the transport and binding of Pb in the blood are discussed.