Abstract
Chloride self-exchange was determined by measuring the rate of 36Cl efflux from human red blood cells at pH 7.2 (0 degrees C) in the presence of fluoride, bromide, iodide, and bicarbonate. The chloride concentration was varied between 10--400 mM and the concentration of other halides and bicarbonate between 10--300 mM. Chloride equilibrium flux showed saturation kinetics. The half-saturation constant increased and the maximum flux decreased in the presence of halides and bicarbonate: the inhibition kinetics were both competitive and noncompetitive. The competitive and the noncompetitive effects increased proportionately in the sequence: fluoride less than bromide less than iodide. The inhibitory action of bicarbonate was predominantly competitive. The noncompetitive effect of chloride (chloride self-inhibition) on chloride transport was less dominant at high inhibitor concentrations. Similarly, the noncompetitive action of the inhibitors was less dominant at high chloride concentrations. The results can be described by a carrier model with two anion binding sites: a transport site, and a second site which modifies the maximum transport rate. Binding to both types of sites increases proportionately in the sequence: fluoride less than chloride less than bromide less than iodide.
Full Text
The Full Text of this article is available as a PDF (770.0 KB).
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Cass A., Dalmark M. Equilibrium dialysis of ions in nystatin-treated red cells. Nat New Biol. 1973 Jul 11;244(132):47–49. doi: 10.1038/newbio244047a0. [DOI] [PubMed] [Google Scholar]
- DIXON M. The determination of enzyme inhibitor constants. Biochem J. 1953 Aug;55(1):170–171. doi: 10.1042/bj0550170. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Dalmark M., Wieth J. O. Temperature dependence of chloride, bromide, iodide, thiocyanate and salicylate transport in human red cells. J Physiol. 1972 Aug;224(3):583–610. doi: 10.1113/jphysiol.1972.sp009914. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Funder J., Wieth J. O. Potassium, sodium, and water in normal human red blood cells. Scand J Clin Lab Invest. 1966;18(2):167–180. doi: 10.3109/00365516609051812. [DOI] [PubMed] [Google Scholar]
- Gunn R. B., Dalmark M., Tosteson D. C., Wieth J. O. Characteristics of chloride transport in human red blood cells. J Gen Physiol. 1973 Feb;61(2):185–206. doi: 10.1085/jgp.61.2.185. [DOI] [PMC free article] [PubMed] [Google Scholar]
- HOFSTEE B. H. Non-inverted versus inverted plots in enzyme kinetics. Nature. 1959 Oct 24;184:1296–1298. doi: 10.1038/1841296b0. [DOI] [PubMed] [Google Scholar]