Studies on the extractability of brain gangliosides

Abstract

Ganglioside extractability from rat brain homogenates by chloroform/methanol can be selectively reduced by lowering the tissue concentration of monovalent cations by dialysis or washing. In this study, no specificity for either Na+ or K+ is observed, either during dialysis or on the addition of these ions to deionized tissues. Charged organic amines are most effective in restoring ganglioside extract-ability when they have a structure analogous to choline or isopropylamine. The presence of a negative charge close to the nitrogen markedly reduces their effectiveness. Lowering the pH of normal and deionized microsomal preparations prior to extraction also decreases ganglioside extractability, with a minimum at pH 2.5 and a return of extractability at pH 0.5–1.0. A slight return of extractability in deionized preparations is observed in the alkaline range. It is proposed that lowering the tissue pH or decreasing the tissue content of monovalent cations allows an electrostatic association between the negatively charged ganglioside and positively charged groups on proteins.