Flow cytometric measurements and electron microscopy of cell surface glycosaminoglycans using acridine orange

Cell surface glycosaminoglycans (GAGs) were measured, after various treatments, by their binding to Acridine Orange using flow cytometry. Using a critical electrolyte concentration and combining it with specific degradation of individual GAG elements, it was found possible to differentiate between GAG components. The technique was adapted for electron microscopy level to reveal characteristics of membrane-associated GAG. By this means, the cell membrane of the human leukaemic cell line K562 was shown to contain a large amount of GAG; 75% of it was highly sulphated GAG, mostly heparan sulphate. This component was evenly distributed in the outer plasma membrane layer. In the presence of other GAGs, the appearance of complex proteoglycan granules was detected.