Kinetics of DIDS inhibition of swelling-activated K-Cl contrasport in low K sheep erythrocytes |
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Authors: | E. Delpire P. K. Lauf |
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Affiliation: | (1) Department of Physiology and Biophysics, School of Medicine, Wright State University, 45401-0927 Dayton, Ohio |
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Abstract: | Summary The inhibitory effect of various stilbene disulfonates was examined on the swelling-activated Cl-dependent K transport (K-Cl cotransport) in low K sheep erythrocytes. Both diisothiocy-anatostilbenes H2DIDS and DIDS were found to be potent inhibitors. The DIDS concentration yielding 50% inhibition (IC50) of KCl cotransport was 60 m in the absence of external K and 3 m at physiological K concentration. Other stilbene derivatives, such as SITS (4-acetamido-4 isothiocyanatostilbene-2,2-disulfonic acid), were only effective in the presence of external K, whereas DNDS (4,4-dinitrostilbene-2,2-disulfonic acid) and ISA (4-sulfophenyl isothiocyanate) had only slight effects at a concentration of 1 mm. The augmenting effect of external K is due to a second K site, distinguishable from the K transport site by its much higher affinity. No inhibition occurred in the absence of external Cl, whether or not external Rb(K) was present. Additionally, DIDS inhibited K-Cl cotransport activated by thiol alkylation with N-ethylmaleimide (NEM) as well as by Mg depletion in the presence of A23187 and a chelator. We conclude that allosteric sites affect the stilbene binding. When these sites are saturated, changes in external K or Cl concentration do not affect the affinity for DIDS (noncompetitive inhibition).This work was supported by grants in aid from the American Heart Association. |
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Keywords: | K-Cl cotransport stilbenes inhibition sheep erythrocytes volume-activation N-ethylmaleimide A23187 |
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