Intracellular free zinc and zinc buffering in human red blood cells.
Zn2+ has been allowed to equilibrate across the red cell membrane using two agents that increase membrane permeability to this ion: the ionophore A23187 and the specific carrier ethylmaltol. Extracellular free Zn2+ was controlled with EGTA (1,2-di(2-aminoethoxy)ethane-NNN'N'tetra-acetic acid] buffers, except in the case of ethylmaltol, which itself acts as a buffer. Measurement of cellular zinc content at different levels of free Zn2+ facilitated the study of intracellular Zn2+ binding. It was also possible to estimate intracellular free Zn2+ concentration in untreated cells using a "null-point" technique. Intracellular zinc was found to consist of an inexchangeable component of about 129 mumol/10(13) cells and an exchangeable component of 6.7 +/- 1.5 mumol/10(13) cells, with a free concentration of about 2.4 x 10(-11) M. The main component of Zn2+ buffering is hemoglobin, with a dissociation constant of about 2 x 10(-8) M.
Simons
T J
TJ
Biomedical Sciences Division, King's College London.
D001665:Binding Sites; D002021:Buffers; D000001:Calcimycin / Q000494:pharmacology; D002463:Cell Membrane Permeability; D004533:Egtazic Acid / Q000494:pharmacology; D004910:Erythrocyte Membrane / Q000378:metabolism; D004912:Erythrocytes / Q000378:metabolism*; D006801:Humans; D008274:Magnesium / Q000494:pharmacology; D011753:Pyrones / Q000494:pharmacology; D015032:Zinc / Q000097:blood*
D002021:Buffers; D011753:Pyrones; D000001:Calcimycin; D004533:Egtazic Acid; D008274:Magnesium; D015032:Zinc; C052408:ethyl maltol