Ionic effects on the uptake of chloromercuribenzene-p-sulphonic acid by pancreatic islets

Effects of inorganic ions on the uptake of chloromercuribenzene-p-sulphonic acid (CMBS) were studied in microdissected pancreatic islets of non-inbred ob/ob-mice. Na2SO4 stimulated the total islet cell uptake of CMBS but decreased the amount of CMBS remaining in islets after brief washing with L-cysteine. CaCl2 stimulated both the total and the cysteine-nondisplaceable uptake; the stimulatory effect of CaCl2 on the cysteine-non-displaceable CMBS uptake was counteracted by Na2SO4. NaCl, KCl or choline chloride had no significant effect on the total islet cell uptake of CMBS, whereas LiCl was stimulatory. It is concluded that beta-cells resemble erythrocytes in having a permeation path for CMBS that is inhibited by SO4(2-). By analogy with existing models of the erythrocyte membrane, it is suggested that the SO4(2-) sensitive path leads to sulphydryl groups controlling monovalent cationic permeability in beta-cells.