TY - JOUR
T1 - Na+-dependent pH Regulation by the Amitochondriate Protozoan Parasite Giardia intestinalis
AU - Biagini, Giancarlo A.
AU - Knodler, Leigh A.
AU - Saliba, Kevin J.
AU - Kirk, Kiaran
AU - Edwards, Michael R.
N1 - © 2001 ASBMB. Currently published by Elsevier Inc; originally published by American Society for Biochemistry and Molecular Biology.
PY - 2001/8/3
Y1 - 2001/8/3
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=0035800875&partnerID=8YFLogxK
U2 - 10.1074/jbc.M102728200
DO - 10.1074/jbc.M102728200
M3 - Article
SN - 0021-9258
VL - 276
SP - 29157
EP - 29162
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 31
ER -