Intracellular digestion of human erythrocytes by Entamoeba histolytica: a kinetic study in vitro

RESUMO

The objective of this investigation was to quantitatively evaluate, by using light and transmission electron microscopy, the intracellular digesion of human erythrocytes (HE), ingested by Entamoeba histolytica trophozoites in vitro. Amebas fed 10 min with HE were postincubated 3 - 12 h at 36.5ºC without HE, and fixed with glutaraldehyde. After staining by the benzidine reaction, HE per ameba, and percent of amebas containing at least one HE were determined by light microscopy. Trophozoites ingested an average of eight HE per ameba and 92 percent of them contained HE after the 10 min pulse. Erithrocytes were clearly observed as reddish-brown corpuscles in the amebic cytoplasm. During postphagocytosis incubations progressive loss of HE staining, as well as changes in size of food vacuoles, were observed, thus proving the intracellullar digestion of HE. The hydrolysis of HE was corroborated with the electro microscope, the HE cytoplasmic matrix being the first structure catabolized and later the plasma membrane. Quantitative analysis demostrated decrease of 56 percent of ameba containing HE, and 1.35 HE per ameba on average, after 3 h postphagocytosis. Afterwards, both parameters decreased at a slow rate until HEdisappeared. The t ½ of HE witin amebas was 2 h