A QUANTITATIVE ULTRASTRUCTURAL AND CYTOCHEMICAL STUDY OF TPA-INDUCED DIFFERENTIATION IN HL-60 CELLS

The effects of the phorbol ester 12-O-tetradecanoyl phorbol-13-acetate on morphometric and stereological parameters have been studied using the HL-60 cell line as a differentiation model for the monocytic pathw ay. Evaluation of the differentiation was carried out by quantificatio n of endoplasmic reticulum, Golgi apparatus, mitochondria and cytoplas mic granules. Changes in both nuclear and cytoplasmic volumes during T PA-induced differentiation led to a decrease of the nucleus-cytoplasmi c ratio after 3 days of treatment. Plasma membrane glycoprotein patter n was also determined. The major change in cell surface was the presen ce of high amounts of glycoproteins containing N-acetyl glucosamine re sidues that make wheatgerm agglutinin lectin a valuable marker of the monocytic differentiation pathway in HL-60 cells.