5-fluorouracil induces autophagic degeneration in rat oral keratinocytes

In this study, we investigated the effect of 5-fluorouracil (S-FU) on the k eratinocytes of oral epithelium. Female Lewis rats were given 5-FU i.v. and were killed 12, 24 or 36 h after injection. The buccal mucosa was dissecte d. The number of nuclei with DNA strand breaks and the total number of nucl ei per volume of the epithelial basal cell layer was estimated using termin al deoxynucleotidyl transferase (TdT)-mediated deoxyuridine triphosphate (d UTP)-biotin nick end labeling. Epithelial cells were analysed by flow cytom etry, transmission electron microscopy and a dye exclusion test. The number of cells with DNA strand breaks increased in S-FU treated rats. Flow cytom etry showed a decrease in cell size and an increase in granularity with inc reasing doses of 5-FU. Dye exclusion gave no indication of degenerate cell membranes. By transmission electron microscopy, the cells showed evidence o f degeneration, shrinkage and loss of cell-to-cell contact. Vacuolation was extensive and, in contrast to apoptotic cells, nuclear chromatin condensat ion seemed to occur centrally in the nuclei. The results show that 5-FU tre atment in vivo induces alterations in rat oral keratinocytes that are consi stent with autophagic degeneration. (C) 2001 Elsevier Science Ltd. All righ ts reserved.