Membrane internalization processes in different stages of Schistosoma mansoni as shown by a styryl dye (Frei Mao 1–43)

<jats:p>We have used a styryl dye FM 1–43 that cannot cross membranes passively to evaluate membrane vesicle internalization processes from the heptalaminate surface membrane in schistosomula and adult <jats:italic>Schistosoma mansoni</jats:italic>. The process of dye internalization was faster in adult worms than in 3 h skin or 24-h-old mechanically transformed schistosomula. Dye internalization and vesicle formation were inhibited at low temperature which suggests that the process is energy dependent. Dye internalization was observed to be a result of vesicle formation. This process is impaired by primaquine independently of the parasite stage. The specific Ca<jats:sup>2+</jats:sup> chelator EGTA affected dye internalization at a concentration of 5 mm. When parasites were labelled in the presence of genistein (a tyrosine kinase inhibitor) uptake of the dye was blocked in 24-h-old schistosomula. However, only a partial blockage of the dye internalization was seen in adult worms. These results suggest that dye internalization mediated by tyrosine kinase signalling is developmentally regulated.</jats:p>