Evaluating the validity of blood-based membrane potential changes for the identification of bipolar disorder I

An Examination of Blood Cell Membrane Potential as a Diagnostic Test of Attention Deficit Disorder in Children

Objective: To reexamine previous findings that reported that blood cells' membrane potential ratios (MPRs™) differ between youth with ADHD and controls and to determine whether psychostimulants affect MPRs™. Method: Forty-four youth (ages 6-17) with ADHD (not currently taking psychostimulants; n = 24) and controls (n = 20) completed the Mini-International Neuropsychiatric Interview 7 (MINI 7) and a blood draw to determine MPR™. Youth with ADHD provided another blood draw 30 days after receiving psychostimulants. Results: MPR™ values of participants with ADHD who were not taking stimulants were not significantly different from those of the controls. MPR's™ sensitivity was 79.2% and specificity 25.0%. Among youth with ADHD, there was a trending association between lower MPRs™ and taking stimulants (compared with baseline). Conclusion: Results neither replicate prior findings nor support MPRs'™ utility in diagnosing ADHD in youth. We identified possible MPR™ changes after participants with ADHD began stimulants. Further studies are needed to establish the clinical significance of this finding.

Effect of ethacrynic acid on the sodium- and potassium-activated adenosine triphosphatase activity and expression in Old Order Amish bipolar individuals

BACKGROUND

There are numerous reports of abnormalities in the expression of the sodium- and potassium-activated adenosine triphosphatase (Na,K-ATPase) in response to an ionic stress with ethacrynic acid (ECA) challenge in bipolar subjects. However, all of these studies have been in out-bred populations. In an attempt to reduce the genetic variability associated with this observation, we examined this phenomenon within an isolated breeding population.

METHODS

We studied 36 lymphoblastoid cell lines obtained from Old Order Amish individuals who had bipolar disorder, type I (16), or were unaffected siblings of the same gender (9) or unrelated normal controls(11). Cells were treated with 10(-)(5)M ECA for 3 days after which Na,K-ATPase alpha1 protein expression and activity ([(3)H]-ouabain binding, (86)Rb-uptake, and intracellular sodium and potassium concentrations) were measured.

RESULTS

Cells from bipolar patients expressed less Na,K-ATPase as measured by immunoblot analysis after ECA treatment (0.94 + or - SD 0.13 relative units) compared to unaffected siblings (1.06 + or - 0.12, P = 0.029) and Old Order Amish normal controls (1.06 + or - 0.14, P = 0.0004). None of the other variables studied were different.

LIMITATIONS

This is a study of peripheral cells which do not express all of the Na,K-ATPase expressed in the brain. The observed difference is small.

CONCLUSIONS

Ethacrynic-acid-stimulated lymphoblast sodium pump expression in Old Order Amish bipolar subjects is reduced compared to Amish controls.