Na+-dependent pH Regulation by the Amitochondriate Protozoan Parasite Giardia intestinalis

Giancarlo A. Biagini*, Leigh A. Knodler, Kevin J. Saliba, Kiaran Kirk, Michael R. Edwards

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    9 Citations (Scopus)

    Abstract

    Giardia intestinalis is a pathogenic fermentative parasite, which inhabits the gastrointestinal tract of animals and humans. G. intestinalis trophozoites are exposed to acidic fluctuations in vivo and must also cope with acidic metabolic endproducts. In this study, a combination of independent techniques (31P NMR spectroscopy, distribution of the weak acid pH marker 5,5-dimethyl-2,4-oxazolidinedione (DMO) and the fluorescent pH indicator 2′,7′-bis (carboxyethyl)-5,6-carboxyfluorescein (BCECF)) were used to show that G. intestinalis trophozoites exposed to an extracellular pH range of 6.0-7.5 maintain their cytosolic pH (pHi) within the range 6.7-7.1. Maintenance of the resting pHi was Na+-dependent but unaffected by amiloride (or analogs thereof). Recovery of pHi. from an intracellular acidosis was also Na+-dependent, with the rate of recovery varying with the extracellular Na+ concentration in a saturable manner (Km = 18 mM; Vmax = 10 mM H+ min-1). The recovery of pH1 from an acid load was inhibited by amiloride but unaffected by a number of its analogs. The postulated involvement of one or more Na+/H+ exchanger(s) in the regulation of pHi in G. intestinalis is discussed.

    Original languageEnglish
    Pages (from-to)29157-29162
    Number of pages6
    JournalJournal of Biological Chemistry
    Volume276
    Issue number31
    DOIs
    Publication statusPublished - 3 Aug 2001

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