Plasmodium berghei: the use of discontinuous urografin density gradients for the separation of exoerythrocytic malaria parasites.

Urografin was used in the lower cushion of discontinuous density gradient systems, for the separation of human hepatoma cells (Hep G2) infected with exoerythrocytic P. berghei forms from uninfected cells. The hepatoma cells exhibited a rather heterogeneous density distribution, masking the possible density differences between infected and uninfected cells and hindering the efficient separation of both cell types. Purely osmotic damage caused by Urografin on human erythrocytes and hepatoma cells is very limited. On the other hand, the direct toxic effects on P. falciparum blood stages and on P. berghei exoerythrocytic stages are very pronounced. The growth of the former forms is partially inhibited after a pretreatment, but remains acceptable if the contact with Urografin is relatively short. It is almost completely blocked during permanent incubation. The latter forms are killed after 1 hour of contact with Urografin.