Patterns in effects of sulfhydryl reagents on transport in bovine lens

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Abstract
Active fluxes of Na+ and Rb+ and mediated transport of organic nutrients in the bovine lens were inhibited by 5 SH reagents, whereas that of inorganic ions was increased, with the exception of the ouabain-resistant component of Na+, which was not significantly altered. The changes produced by the reagents indicate that cysteinyl residues are essential for normal operation of most of the transport systems investigated. The variable effectiveness of the reagents on transport of some of the solutes may provide information on the microenvironment of critical SH residues in the transporters: that for glucose, adenosine and influx of Ca2+ appears to be hydrophobic; for acetate and influx of Na+, hydrophilic. Comparison of the rates of inactivation of influx via the L-system of 1-aminocyclopentane-1-carboxylate indicates that p-chloromercuriphenylsulfonate is most effective, inhibiting almost completely in 10 min. There was no significant lag in inhibition by the selective glutathione oxidants, tert-butylhydroperoxide and diazinedicarboxylic acid-bis(N,N-dimethylamide), indicating that they either rapidly oxidize glutathione in superficial cellular elements, or, less probaly, act directly on the transporter.