Alteration of erythrocyte phosphate transport in primary depressive disorders

Chronic myo-inositol increases rat brain phosphatidylethanolamine plasmalogen

BACKGROUND

Oral myo-inositol (12--18 g/day) has shown beneficial effect in placebo-controlled studies of major depression, panic disorder, and obsessive compulsive disorder, and preliminary data suggest it also may be effective in bipolar depression. Evidence linking antidepressant activity to membrane phospholipid alterations suggested the examination of acute and chronic myo-inositol effects on rat brain membrane phospholipid metabolism.

METHODS

With both (31)P nuclear magnetic resonance (NMR) and quantitative high-performance thin-layer chromatography (HPTLC; hydrolysis) methods, rat brain phospholipid levels were measured after acute (n = 20, each group) and chronic myo-inositol administration (n = 10, each group). With (31)P NMR, we measured myo-inositol rat brain levels after acute and chronic myo-inositol administration.

RESULTS

Brain myo-inositol increased by 17% after acute myo-inositol administration and by 5% after chronic administration, as compared with the control groups. Chronic myo-inositol administration increased brain phosphatidylethanolamine (PtdEtn) plasmalogen by 10% and decreased brain PtdEtn by 5%, thus increasing the ratio PtdEtn plasmalogen (PtdEtn-Plas)/PtdEtn by 15%. Phosphatidylethanolamine plasmalogen levels quantified by (31)P NMR and HPTLC were highly correlated. The validity and reliability of the (31)P NMR method for phospholipid analysis were demonstrated with phospholipid standards.

CONCLUSIONS

The observed alteration in the PtdEtn-Plas/PtdEtn ratio could provide insights into the therapeutic effect of myo-inositol in affective disorders.

Osmotic behavior of erythrocytes from patients with a major affective disorder. A freeze-fracture electron microscopic study

Previously we have demonstrated a state-dependent decrease in the number of membrane vesicles in erythrocytes from patients with a major depressive episode. We now report an increase in the number of membrane vesicles during a manic episode as well as a reduction during lithium treatment and we also present data suggesting that the number of erythrocyte membrane vesicles in the affective disorders is dependent on osmotic shrinkage due to the freezing for freeze-etch electron microscopy. Although caution is required since the interrater reliability of the measurement of osmotic strain was insufficient in the mid range where it was tested, we do not think this invalidates the differences in osmotic strain found in the low and high ranges during depressive and manic episodes respectively. These findings warrant the use of more precise techniques in studies of the osmotic behavior of erythrocytes from patients with a major affective disorder.

Search for abnormal proteins in erythrocytes and plasma from patients with a major depressive episode

A sensitive double-label two dimensional gel electrophoresis procedure has been used to search for abnormal proteins in plasma and erythrocyte plasma membranes from patients with major depressive illness. For both plasma and erythrocytes, minor qualitative and quantitative differences between the proteins in pooled samples from depressed and normal subjects were observed; however, these were shown to be artifacts and no consistent differences were found.

Decreased erythrocyte membrane elevations in patients with a major depressive episode

Washing of erythrocytes from healthy volunteers in an isotonic sodium chloride solution at pH 5.6 results in the occurrence of plasma membrane elevations as observed in freeze-etch electron microscopy. This is prevented by anion permeability inhibiting agents. In the absence of these agents a reduced number of elevations was found in 23 of 36 patients with a major depressive episode. This reduced capacity to form membrane elevations was positively correlated with a genetic vulnerability, defined as an admission to a psychiatric hospital in first-degree relatives.