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New drugs for the Na+/H+ exchanger : Influence of Na+ concentration and determination of inhibition constants with a microphysiometer

Fischer, H. and Seelig, A. and Beier, N. and Raddatz, P. and Seelig, J.. (1999) New drugs for the Na+/H+ exchanger : Influence of Na+ concentration and determination of inhibition constants with a microphysiometer. The Journal of Membrane Biology, 168 (1). pp. 39-45.

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Official URL: http://edoc.unibas.ch/dok/A5257421

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Abstract

The NHE-1 isoform of the Na+/H+ exchanger is excessively activated in cardiac cells during ischemia. Hence NHE-1 specific inhibitors are being developed since they could be of beneficial influence under conditions of cardiac ischemia and reperfusion. In this study, the Cytosensortrade mark microphysiometer was used to measure the potency of four new drug molecules, i.e., EMD 84021, EMD 94309, EMD 96785 and HOE 642 which are inhibitors of the isoform 1 of the Na+/H+ exchanger. The experiments were performed with Chinese hamster ovary cells (CHO K1) which are enriched in the NHE-1 isoform of the Na+/H+ antiporter. The Na+/H+ exchanger was stimulated with NaCl and the rate of extracellular acidification was quantified with the Cytosensor. The proton exchange rate was measured as a function of the NaCl concentration in the range of 10-138 mm NaCl stimulation. The proton exchange rate followed Michaelis-Menten kinetics with a KM = 30 +/- 4 mm for Na+. Addition of either one of the four inhibitors decreased the acidification rate. The IC50 values of the four compounds could be determined as 23 +/- 7 nm for EMD 84021, 5 +/- 1 nm for EMD 94309, 9 +/- 2 nm for EMD 96785 and 8 +/- 2 nm for HOE 642 at 138 mm NaCl, in good agreement with more elaborate biological assays. The IC50 values increased with the NaCl concentration indicating competitive binding of the inhibitor. The microphysiometer approach is a fast and simple method to measure the activity of the Na+/H+ antiporter and allows a quantitative kinetic analysis of the proton excretion rate.
Faculties and Departments:05 Faculty of Science > Departement Biozentrum > Former Organization Units Biozentrum > Biophysical Chemistry (Seelig A)
05 Faculty of Science > Departement Biozentrum > Former Organization Units Biozentrum > Biophysical Chemistry (Seelig J)
UniBasel Contributors:Seelig, Joachim and Seelig-Löffler, Anna
Item Type:Article, refereed
Article Subtype:Research Article
Bibsysno:Link to catalogue
Publisher:Springer-Verlag
ISSN:0022-2631
e-ISSN:1432-1424
Note:Publication type according to Uni Basel Research Database: Journal article
Language:English
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Last Modified:14 Nov 2017 11:06
Deposited On:22 Mar 2012 13:18

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