ISSN:
1432-1424
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Summary The fluorescent probe ANS is a permeant anion in human red cells. The rate of ANS permeation is decreased by lyotropic anions and increased by low ionic strength, resembling the response of Cl and SO4 transport to changes in the composition of the medium. ANS inhibits Cl and SO4 exchange measured at 0 and 37°C, respectively. The inhibitory potency of ANS isomers increases in the sequence 1,8 ANS〈2,8 ANS〈1,4 ANS〈2,6 TNS〈5,2 ANS. The disulfonic stilbene derivative SITS inhibits Cl exchange 50%. Combinations of ANS and SITS result in additive inhibitory effects regardless of the ANS concentration. Combinations of dipyridamole and ANS show additive inhibitory effects only at low concentrations of the latter. The mechanisms of inhibition by ANS are discussed in terms of (1) interactions between the probe and an anion carrier and (2) modifications of the membrane surface charge by ANS. Assuming that ANS bound to the membrane surface produces a negative surface charge, ANS-dependent surface potentials of magnitude sufficient to account for the observed inhibition can be calculated using double layer theory. It is suggested that anionic amphiphiles inhibit anion and increase cation permeability through modifications of surface charge that alter the ion concentrations at the permeability barriers and a second step, affected by SITS, is involved in anion permeation.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01872408
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