Abstract
1. Zinc is taken up into human red cells by two mechanisms that depend upon the presence of anions. One of these requires bicarbonate ions, is inhibited by 4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS) and appears to be catalysed by the anion exchanger. The second occurs in the presence of thiocyanate or salicylate ions and may represent transport of a neutral complex with Zn2+. 2. The initial rate of Zn2+ uptake via the anion exchanger is 64 +/- 13 mumol (10(13) cells x h)-1 microM-1 external Zn2+, in the presence of 5 mM-bicarbonate at pH 7.4 and 37 degrees C (+/- S.D.). This is about 1/250 of the corresponding rate of Pb2+ uptake by the anion exchanger. 3. The variation of transport with Zn2+ concentration, HCO3- concentration and pH suggests that the transported species may be ZnCO3Cl- or Zn(HCO3)Cl.OH-. 4. Zinc efflux could not be observed by either of the above routes. This observation suggests that the intracellular free Zn2+ concentration is below 3 nM.