title: Neutrophil intracellular pH and Na+/H+ exchanger activity in pre-eclampsia.
abstract: Elevated Na(+)/H(+) exchanger activity and intracellular acidosis have previously been demonstrated in white blood cells isolated from women who have suffered from a pre-eclamptic pregnancy. The mechanisms underlying this abnormality and the implications in pre-eclamptic pregnancies are, at present, unclear. In this study, we used neutrophils from third trimester pre-eclamptic patients and third trimester normotensive pregnant controls to determine Na(+)/H(+) exchanger isoform-1 (NHE-1) activity and intracellular pH. This was performed using a well-validated technique involving flurometry and a pH sensitive dye, 2,7'Bis-(carboxyethyl) 5.6 carboxyfluorescein acetomethyl ester (BCECF-AM). Time course experiments were performed to assess the contribution of plasma factors to intracellular pH measurements. Plasma digoxin-like factor (DLF) was assessed in both patients and normotensive controls. Neutrophil intracellular pH was significantly lower in the pre-eclamptic patients (7.15 +/- 0.050) compared with the normotensive pregnant controls (7.36 +/- 0.027; P<.001). NHE-1 activity (in mmol/L/min) was significantly higher in the pre-eclamptics (32.4 +/- 1.9) compared with the normotensive neutrophils (27.1 +/- 1.6; P =.038). Times course experiments showed that mean pre-eclamptic intracellular pH increased from 7.11 +/- 0.049 to 7.25 +/- 0.043 after 2 hours of incubation. DLF, measured as amount of inorganic phosphate liberated from adenosine triphosphate (ATP), was significantly lower when plasma from the pre-eclamptic patients was incubated with the enzyme compared with plasma from the normotensive pregnant women (54.9 +/- 2.6 nmol/mL plasma v 63.91 +/- 1.7 nmol/mL plasma, n = 6, P =.018 unpaired Student's t test). The results suggest that elevated NHE-1 activity and intracellular acidosis are intermediate phenotypes in women who have pre-eclampsia. Intracellular pH may have been affected by plasma as shown in the time course experiments. DLF, an inhibitor of Na(+)/K(+)ATPase, may contribute to this intracellular acidosis in pre-eclamptic neutrophils.
authors.affiliation: Department of Medicine, Leicester Royal Infirmary, Leicester, UK.
authors.forename: Virginia M
authors.initials: VM
authors.lastname: Lee
authors.forename: Aidan W F
authors.initials: AW
authors.lastname: Halligan
authors.forename: Leong L
authors.initials: LL
authors.lastname: Ng
mesh_terms: D000328:Adult; D002021:Buffers; D002298:Cardenolides; D004077:Digoxin / Q000097:blood; D004777:Environment; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D009504:Neutrophils / Q000378:metabolism*; D010710:Phosphates / Q000097:blood; D011225:Pre-Eclampsia / Q000378:metabolism*; D011247:Pregnancy; D012503:Saponins / Q000097:blood; D017923:Sodium-Hydrogen Exchangers / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D002021:Buffers; D002298:Cardenolides; D010710:Phosphates; D012503:Saponins; D017923:Sodium-Hydrogen Exchangers; C034504:digoxin-like factors; D004077:Digoxin