The effects of maleic anhydride on the ionic permeability of red cells

Maleic anhydride (MA) has been shown to react specifically and rapidly with amino groups of proteins; the maleyl amino groups are negatively charged and completely stable at neutral pH. Treatment of human red cells with this reagent results in a significant increase in K(+) permeability which is associated with a much smaller increase in Na(+) permeability. Opposite effects are observed on anion permeability, the SO 4 (--) and Cl(-) permeability being decreased to an approximately similar extent upon treatment with MA.Studies on the distribution of MA between membrane lipids and proteins shows that most of the membrane-bound MA is associated with membrane proteins. These results suggest that the observed effects of MA on the ion permeability of the red cell are caused by its combination with amino groups of cell membrane proteins.