Effect of hypoxia on the superficially exposed carbohydrates of subcellular fractions of guinea pig cerebral cortex.

Experimental hypoxia led to changes in carbohydrate-containing macromolecules located on the microsomal and synaptosomal membrane surface. It was found that hypoxia reduced the external membrane-bound sialic acid content in microsomal and synaptosomal fractions. On the other hand, a decrease in fucose content of proteins in hypoxic synaptosomal fraction was found. Similarly, a decrease was observed in the amount of 3H-labeled concanavalin A bound to the microsomal and synaptosomal glycoprotein fractions. Treatment of microsomal and synaptosomal fractions with galactose oxidase followed by reduction with tritiated potassium borohydride resulted in a significantly higher incorporation rate of tritium into the hypoxic membranes. This was accompanied by an increase in the endogenous glycoprotein galactose transferase activity both in microsomal and synaptosomal fractions.