title: Measuring pH of the Plasmodium falciparum digestive vacuole by flow cytometry.
abstract: Studies show that the pH of the malaria parasite's digestive vacuole (DV) plays a key role in the physiological functions of this organelle and antimalarial drug accumulation, and yet is technically difficult to measure. In this study, a flow cytometry-based technique was developed to measure the DV pH using a ratiometric pH indicator, FITC-dextran loaded into the DV of saponin-permeabilized parasites. To calculate the DV pH, a standard pH calibration curve was generated by incubating the saponin-permeabilized cells in buffers with different pH in the presence of an ionophore, CCCP. The measured average pH of the DV was 5.27 ± 0.03 that is approximately the same in the parasites observed microscopically by Hayward et al. (2006) (5.50 ± 0.14) using the same probe. The removal of glucose from the medium, causing a rapid depletion of parasite ATP, resulted in an alkalization of the DV. The DV was reacidified upon restoration of glucose to the medium. This technique provides a rapid, simple and quantitative measurement of the DV pH on a large number of cells. It will also be useful in future attempts to evaluate the effect of antimalarial drugs (i.e. chloroquine and artemisinin-based drugs) in pH changes of the DV.
authors.affiliation: School of Health Sciences, Health Campus, Universiti Sains Malaysia, 16150 Kubang Kerian, Kelantan, Malaysia.
authors.forename: Nurhidanatasha
authors.initials: N
authors.lastname: Abu Bakar
mesh_terms: D003470:Culture Media / Q000737:chemistry; D005434:Flow Cytometry / Q000379:methods*; D005947:Glucose / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D010274:Parasitology / Q000379:methods*; D010963:Plasmodium falciparum / Q000737:chemistry*; D013194:Staining and Labeling / Q000379:methods; D014617:Vacuoles / Q000737:chemistry*
chemical_list: D003470:Culture Media; D005947:Glucose