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. 1980 Dec;32(3):907–920. doi: 10.1016/S0006-3495(80)85025-9

Stoichiometry and apparent dissociation constant of the calcium-arsenazo III reaction under physiological conditions.

Z Ahmed, L Kragie, J A Connor
PMCID: PMC1327380  PMID: 7260310

Abstract

In vitro and in situ tests have been run to characterize the reaction of the mettalochromic indicator, arsenazo III, with calcium. Job plots as well as plots of indicator absorbance vs. [Ca2+] at different indicator concentrations show a 1:1 reaction stoichiometry. Equilibrium analysis and analysis using Adair's equation are also consistent with 1:1 complexes being formed and give estimates of 34 and 45 muM for the apparent dissociation constant. In situ tests were carried out using giant neurons from Archidoris monteryensis, a marine gastropod mollusc. Dye absorbance changes were measured during voltage clamp pulses which produced a fixed calcium influx. The dependence of absorbance change on total dye concentration is consistent with the formation of a 1:1 complex of Ca with ArIII if measurements are made during the initial period of the loading pulse, less than 300 ms, although the apparent dependency changes with longer delay in measurements from the onset of the pulse.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Ahmed Z., Connor J. A. Intracellular pH changes induced by calcium influx during electrical activity in molluscan neurons. J Gen Physiol. 1980 Apr;75(4):403–426. doi: 10.1085/jgp.75.4.403. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Ahmed Z., Connor J. A. Measurement of calcium influx under voltage clamp in molluscan neurones using the metallochromic dye arsenazo III. J Physiol. 1979 Jan;286:61–82. doi: 10.1113/jphysiol.1979.sp012607. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Brinley F. J., Jr, Tiffert T., Scarpa A., Mullins L. J. Intracellular calcium buffering capacity in isolated squid axons. J Gen Physiol. 1977 Sep;70(3):355–384. doi: 10.1085/jgp.70.3.355. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Brown J. E., Brown P. K., Pinto L. H. Detection of light-induced changes of intracellular ionized calcium concentration in Limulus ventral photoreceptors using arsenazo III. J Physiol. 1977 May;267(2):299–320. doi: 10.1113/jphysiol.1977.sp011814. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Brown J. E., Cohen L. B., De Weer P., Pinto L. H., Ross W. N., Salzberg B. M. Rapid changes in intracellular free calcium concentration. Detection by metallochromic indicator dyes in squid giant axon. Biophys J. 1975 Nov;15(11):1155–1160. doi: 10.1016/S0006-3495(75)85891-7. [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. Coles J. A., Brown J. E. Effects of increased intracellular pH-buffering capacity on the light response of Limulus ventral photoreceptor. Biochim Biophys Acta. 1976 Jun 4;436(1):140–153. doi: 10.1016/0005-2736(76)90226-1. [DOI] [PubMed] [Google Scholar]
  7. Connor J. A. Calcium current in molluscan neurones: measurement under conditions which maximize its visibility. J Physiol. 1979 Jan;286:41–60. doi: 10.1113/jphysiol.1979.sp012606. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Connor J. A. Time course separation of two inward currents in molluscan neurons. Brain Res. 1977 Jan 7;119(2):487–492. doi: 10.1016/0006-8993(77)90330-4. [DOI] [PubMed] [Google Scholar]
  9. Dipolo R., Requena J., Brinley F. J., Jr, Mullins L. J., Scarpa A., Tiffert T. Ionized calcium concentrations in squid axons. J Gen Physiol. 1976 Apr;67(4):433–467. doi: 10.1085/jgp.67.4.433. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Geduldig D., Gruener R. Voltage clamp of the Aplysia giant neurone: early sodium and calcium currents. J Physiol. 1970 Nov;211(1):217–244. doi: 10.1113/jphysiol.1970.sp009276. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. Gorman A. L., Thomas M. V. Changes in the intracellular concentration of free calcium ions in a pace-maker neurone, measured with the metallochromic indicator dye arsenazo III. J Physiol. 1978 Feb;275:357–376. doi: 10.1113/jphysiol.1978.sp012194. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Meech R. W. Calcium-dependent potassium activation in nervous tissues. Annu Rev Biophys Bioeng. 1978;7:1–18. doi: 10.1146/annurev.bb.07.060178.000245. [DOI] [PubMed] [Google Scholar]
  13. Meech R. W. The sensitivity of Helix aspersa neurones to injected calcium ions. J Physiol. 1974 Mar;237(2):259–277. doi: 10.1113/jphysiol.1974.sp010481. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Miledi R., Parker I., Schalow G. Calcium transients in frog slow muscle fibres. Nature. 1977 Aug 25;268(5622):750–752. doi: 10.1038/268750a0. [DOI] [PubMed] [Google Scholar]
  15. Ohnishi S. T. A method of estimating the amount of calcium bound to the metallochromic indicator arsenazo III. Biochim Biophys Acta. 1979 Aug 22;586(2):217–230. doi: 10.1016/0304-4165(79)90094-1. [DOI] [PubMed] [Google Scholar]
  16. Thomas M. V. Arsenazo III forms 2:1 complexes with Ca and 1:1 complexes with Mg under physiological conditions. Estimates of the apparent dissociation constants. Biophys J. 1979 Mar;25(3):541–548. doi: 10.1016/S0006-3495(79)85322-9. [DOI] [PMC free article] [PubMed] [Google Scholar]
  17. Tillotson D. Inactivation of Ca conductance dependent on entry of Ca ions in molluscan neurons. Proc Natl Acad Sci U S A. 1979 Mar;76(3):1497–1500. doi: 10.1073/pnas.76.3.1497. [DOI] [PMC free article] [PubMed] [Google Scholar]

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