Effect of sulfhydryl-reactive reagents on water transport

The transport of water in certain mammalian red cells as well as other cells and tissues has been shown to be inhibited by certain sulfhydryl-reactive reagents [4,10,29]. A summary of these studies is given in Table 3. Half-maximal inhibition is produced at a concentration of 0.02 mM. With certain inhibitors this inhibition develops slowly and is fully reversible by treatment with excess amount of cysteine or glutathione. As stated earlier, the finding that Pi/P 1 is one of the most compelling pieces of evidence for the existence of pores . In the presence of PCMBS, P[ =Pd suggesting that this compound acts by shutting off these pores . 

Effect of /)-chloromcrcuriphenyl sulfonate (PCMBS) on the permeability coeffieients of membranes and tissues to water  

The permeability coefficients of most mammalian red cell membranes to water under control conditions are normally 10 times higher than the corresponding value for lecithin cholesterol bilayers [30], In the presence of sulfhydryl-reactive reagents, the permeability coefficients of the two membranes are practically identical, which suggests that these reagents act by blocking the proposed aqueous pores leaving the lipid bilayer of the mammalian red-cell membranes as the only alternative route for water transport. 

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