Differential Uptake of Horseradish Peroxidase Isoenzymes by Cultured Neuroblastoma Cells

Abstract

The endocytotic uptake snd intracellular decay of horseradish peroxidase isoenzymes C and A by cultured mouse neuroblastoma cells were analyzed quantitatively by a direct spectrophotometric assay. At concentrations below 1 mg/ml the rate of uptake of the isoenzyme C was more than 3 times as much as the isoenzyme A. This differential uptake suggests horseradish peroxidase is not only endocytosed in the nonselective fluid phase. The implication of this selectivity in the biological significance of retrograde axonal transport of proteins by neuronal systems is discussed.