Altered Na+/H+ exchanger isoform 1 activity in immortalized lymphoblasts from women with pre-eclampsia: evidence for an intermediate phenotype.
Previous studies have demonstrated a raised Na(+) content in leucocytes isolated from women with pre-eclampsia. Increased Na(+)/H(+) exchanger activity is one membrane transport abnormality that may contribute to this phenomenon and may be implicated in the abnormal volume homoeostasis and hypertension associated with the disease. Increased Na(+)/H(+) exchanger activity has been documented in nucleated white blood cells from both pre-eclamptic and post-partum pre-eclamptic women, and may suggest the importance of genetic influences on exchanger activity. In the present study, we used lymphoblasts from women with pre-eclampsia and from age- and gestation-matched normotensive pregnant controls to determine Na(+)/H(+) exchanger activity and intracellular resting pH using fluorimetry and the pH-sensitive dye BCECF-AM [bis(carboxyethyl)carboxyfluorescein acetoxymethyl ester]. Determination of Na(+)/H(+) exchanger protein abundance was performed by Western blotting. Intracellular pH was not significantly different in cells from pre-eclamptic women compared with those from normotensive controls. Na(+)/H(+) exchanger activity was measured when the intracellular pH was clamped at 6.0, and was found to be significantly higher in cells from pre-eclamptic women (20.77+/-0.92 mmol x min(-1) x l(-1)) compared with those from normotensive controls (15.22+/-0.92 mmol x min(-1) x l(-1); P =0.001). Na(+)/H(+) exchanger protein abundance was established to be similar in the two subject groups, suggesting that the turnover number for the Na(+)/H(+) exchanger is increased in the women with pre-eclampsia. These changes in Na(+)/H(+) exchanger activity indicate the importance of genetic factors in determining this particular phenotype, since in this cell culture model of pre-eclampsia it is likely that environmental or hormonal influences present in vivo would have declined. Overactivity of the Na(+)/H(+) exchanger may contribute to the raised intracellular Na(+) concentration reported previously in white blood cells from women with pre-eclampsia.
Lee
V M
VM
University of Leicester, Division of Medicine and Therapeutics, Level 4, Clinical Sciences Building, Leicester Royal Infirmary, UK.
Quinn
P A
PA
Jennings
S C
SC
Halligan
A W F
AW
Ng
L L
LL
D000328:Adult; D015153:Blotting, Western; D018929:Cell Culture Techniques; D002472:Cell Transformation, Viral; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008214:Lymphocytes / Q000378:metabolism*; D010641:Phenotype; D011225:Pre-Eclampsia / Q000097:blood* / Q000235:genetics; D011247:Pregnancy; D017923:Sodium-Hydrogen Exchangers / Q000097:blood*
D017923:Sodium-Hydrogen Exchangers