Figure 2.

Effect of AA addition on the production of PG by P. falciparum strains. (a) PG production by cell homogenates. P. falciparum FCR3 and Honduras-1 strains were grown in medium with or without the addition of 33 μM AA for 48 h before harvesting. After incubation of the parasite homogenates with 1 mM AA at 37°C for 30 min, PGs produced were measured by EIA. The values shown are from three independent experiments with SE. In a typical experiment, FCR3 culture contained 0, 2.5, and 2.5% of RBCs infected with rings, trophozoites, and schizonts, respectively, and that of Honduras-1 contained 0.8, 3.3, and 1.4% of RBCs with rings, trophozoites, and schizonts, respectively. White, light gray, and dark gray bars represent PGD₂, PGE₂, and PGF_2α, respectively. (b) PG release into the culture medium. FCR3 and Honduras-1 strain cultures initially contained 0.3% of RBCs infected with trophozoites and were cultivated for 48 h in medium (10 ml) with or without 33 μM AA. After 48 h, 0.06, 1.25, and 0.53% of RBCs in the FCR3 culture and 0, 1.1, and 0.1% of RBCs in the Honduras-1 culture were infected with rings, trophozoites, and schizonts, respectively. Cells were collected by centrifugation at 1,800 g for 5 min and washed twice with incomplete medium. Fresh medium containing 33 μM AA was added to the culture, and the parasite cells were incubated for another 2 h. The culture supernatant (8 ml) was then taken and centrifuged at 5,000 g for 30 min at 4°C to remove residual cells. The culture supernatants obtained were assayed for PGs by EIA.