Effects of pH and NaCl Concentration on Binding of Covalently-Linked Insulin Dimers to Liver Plasma Membranes

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Abstract
The effects of NaCl concentration and pH on binding to purified rat liver plasma membranes were compared for labeled insulin and 2 covalently-linked insulin dimers. Specific binding of both dimers and insulin increased as NaCl concentration increased from 0-1 M in 0.05 M Tris/HCl buffer. The initial rise in binding was much greater for dimers than for insulin. Specific binding of dimers was sensitive to pH changes in 0.029 M barbital sodium acetate buffer, but this effect was more marked with insulin, which reached a sharp binding peak at pH 7.7-8.0. Both total and non-specific dimer binding were .apprx. 2-fold greater at pH 5.0 than at pH 8.0. Specific-binding fraction determinations of both dimers relative to insulin were critically dependent on the experimental conditions of Na+/Cl ion concentration and pH. These observations allow a better understanding of the nature of ligand-receptor interaction.

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