| Abstract: | The water permeability of human erythrocytes has been monitored by nuclear magnetic resonance (NMR) before and after treatment of the cells with various sulfhydryl reagents. Preincubation of the cells with N-ethylmaleimide (NEM), a non-inhibitory sulfhydryl reagent, results in a faster and more sensitive inhibition of water exchange by mercurials. The inhibition of water exchange by p-chloromercuribenzene sulfonate (PCMBS) was maximal at a binding of approximately 10 nmol PCMBS per mg protein when non-specific sulfhydryl groups are blocked by NEM. Inhibition by PCMBS has been correlated with the binding of 203Hg to erythrocyte membrane proteins. A significant binding of label to band 3 and the polypeptides in band 4.5 occurs, with approximately 1 mol of mercurial bound per mol of protein. Inhibition of water transport by sulfhydryl reagents does not induce major morphological changes in the cells as assessed by freeze-fracture and scanning electron microscopy. |
