Fig. 5.

Arginase activity of Blastocystis ST-4 (WR-1) and ST-7 (B). (a) Lysate of 6 × 10⁷ Blastocystis ST-7 (B) cells showed significantly higher arginase activity than ST-4 (WR-1) cells (P < 0.01). Five minutes of incubation of the parasite lysates at 95°C completely inhibited arginase activity. (b) Cell-density-dependent increase in arginine degradation by parasite lysate was observed in ST-7 (B), while arginase activity of ST-4 (WR-1) did not change much between lysates of 2 × 10⁷ and 8 × 10⁷ parasites. These findings suggest that higher arginine degradation by Blastocystis ST-7 (B) might be responsible for epithelial iNOS inhibition by Blastocystis ST-7 (B). Each point represents a mean of six samples collected from two independent experiments (each in triplicate). Error bars represent standard errors.