Membrane Na(+)-K+ ATPase mediated cascade in bipolar mood disorder, major depressive disorder, and schizophrenia--relationship to hemispheric dominance.

The isoprenoid pathway produces digoxin, an endogenous membrane Na(+)-K+ ATPase inhibitor and regulator of neurotransmitter transport. The objective of the study was to relate digoxin status and hemispheric dominance to the pathogenesis of psychiatric disorders--bipolar mood disorder, major depressive disorder, and schizophrenia. The following parameters were assessed in bipolar mood disorder during the manic phase and depressive phase of the illness as well as in major depressive disorder, and schizophrenia: HMG CoA reductase activity, tryptophan and tyrosine catabolic patterns, red blood cell (RBC) Na(+)-K+ ATPase activity, and serum magnesium. These parameters were compared to individuals of differing hemispheric dominance. The levels of serum digoxin and HMG CoA reductase activity were found to be decreased in the depressive phase of bipolar mood disorder and major depressive disorder with a corresponding increase in RBC Na(+)-K+ ATPase activity and serum magnesium levels. There was increase in tyrosine and tyrosine catabolites, and a reduction in tryptophan and its catabolites, in the serum in the depressive phase of bipolar mood disorder and major depressive disorder. The neurotransmitter patterns and digoxin levels in the depressive phase of bipolar mood disorder/major depressive disorder correlated with those in right-handed/left hemisphere dominant individual. The neurotransmitter patterns and digoxin levels in the manic phase of bipolar mood disorder and schizophrenia correlated with those in left-handed/right hemisphere dominant individuals. Digoxin status and hemispheric dominance could correlate with the pathogenesis of psychiatric disorders--schizophrenia, major depressive disorder, and bipolar mood disorder.