“Kinetics of molecular transfer across the tegument of protoscoleces and hydatid cysts of Echinococcus granulosus and the relevance of these studies to drug targeting”

Abstract

Protoscoleces of Echinococcus granulosus (horse strain) were found to absorb, by a combination of mediated transport and passive diffusion, 10 L-amino acids, 1 D-amino acid (D-alanine) and D(+)glucose. The L-amino acids enter the protoscolex through four, kinetically distinct, transport systems. Secondary hydatid cysts were also found to absorb and accumulate 4 amino acids, but at a far slower rate than the protoscoleces. Entry into the cyst wall component appears to occur by passive diffusion but, for L-threonine at least, entry into the fluid-filled interior is by mediated transport. A synthetic polymer (PVP) was found to enter the cyst by endocytosis. Analysis of hydatid fluid and host blood indicates that amino acids are accumulated to varying degrees in the cyst, the values obtained resembling those achieved during in vitro experiments. The relevance of these studies to drug targeting is discussed.