Lithium ion transport and affective disorders within families of bipolar patients. Identification of a major gene locus

Hypertension and the genetics of red cell membrane abnormalities

Hypertension represents the upper 15-25% of the blood pressure distribution in industrialized countries. The trait is practically absent in primitive societies and is made manifest by diet and lifestyles in industrialized countries. High blood pressure is an important risk factor for strokes, heart disease and renal disease. The frequency of hypertension is higher among blacks than among whites in the USA. Various twin, family and adoption studies indicate a strong genetic effect on blood pressure. The genetic mechanisms are unknown. Membrane transport variability has been studied in red cells as a surrogate for analogous alterations in smooth muscle or renal cells. Among the various transport systems, erythrocyte sodium-lithium countertransport (CT) has been consistently elevated in variable proportions of Caucasian hypertensives. Genetic studies of countertransport levels have shown familial aggregation and higher concordance for monozygotic than dizygotic twins. Complex segregation analysis suggests the action of a major gene superimposed on a polygenic background. The postulated gene (B) raises CT activity and has a population frequency of 0.25. CT levels of the common AA homozygotes and AB heterozygotes cannot be distinguished from each other, whereas CT activity of BB homozygotes (6% of the population) is significantly elevated. Although the CT gene contributes only 2.7% to 3.5% of the variability of blood pressure over its entire range, 14% to 20% of persons with systolic hypertension (greater than 140 mmHg) are BB homozygotes rather than the expected 6% to 7%. A much lower frequency of elevated countertransport activity among black hypertensives suggests genetic heterogeneity in the pathogenesis of high blood pressure. Further investigations on the mechanism and genetic linkage relationships of the putative CT gene may aid in elucidating an important mechanism of blood pressure elevation and will allow molecular approaches in the future.

Biochemical and psychiatric predictors of Li(+) response and toxicity in Li(+)-treated bipolar patients

BACKGROUND

It has not been determined whether biochemical or psychological variables predict clinical response and toxicity to Li(+) treatment.

METHODS

From 30 Li(+)-treated bipolar patients, we measured biochemical variables in red blood cells (RBCs) that encompassed the cell membrane abnormality and the Li(+)/Mg(2+) competition mechanism. Psychiatric measures of depression, mania, and side effects of Li(+) toxicity were correlated with these biochemical variables. Physician classification of Li(+) response and toxicity for each patient were used for determining whether significant differences in biochemical variables and psychiatric measures existed between full and partial responders, and as well as toxic and non-toxic Li(+)-treated bipolar patients.

RESULTS

Serum [Li(+)] ([Li(+)]e), the ratio of intracellular RBC to serum Li(+), [Li(+)]i/[Li(+)]e, and phosphatidylcholine shared moderate proportions of variance (10-15%) with several of the psychiatric measures. Physician assessment of full response was predicted by higher levels of [Li(+)]e and lower scores on the Hamilton Slowing subscale (95.6% accuracy), whereas higher lithium-binding constants and higher Hamilton total scores perfectly predicted physician classification of partial response. Higher scores on Hamilton Slowing subscale and General Side Effects (GSE) scale were strongly predictive of physician classified Li(+) toxicity (80% accuracy), whereas lower levels of [Li(+)]e and lower scores on the Hamilton Symptom Severity subscale perfectly predicted physician rated non-toxicity in these patients.

CONCLUSIONS

We found distinct [Li(+)]e levels that predict response and/or toxicity. Specifically, when [Li(+)]e was in the range of 0.93-1.42 mM, full response without toxicity was predicted; higher values predicted toxicity; lower values predicted partial response.

Testing competing path models linking the biochemical variables in red blood cells from Li+-treated bipolar patients

OBJECTIVES

Red blood cells (RBCs) from Li+-treated bipolar patients have shown abnormalities in intracellular Li+ concentration ([Li+]i), Na+/Li+ exchange rates, and membrane phospholipid levels. Based on Li+-loaded RBC studies, we hypothesized that Li+-treated bipolar patients also have varied intracellular free Mg2+ concentrations ([Mg2+]f) as compared with normotensive patients. We addressed how these experimentally determined values are intercorrelated. Assuming that Li+ treatment alters these biochemical parameters, we provide hypothetical pathways based upon structural equation modeling statistics.

METHODS

In RBCs from 30 Li+-treated bipolar patients, we determined [Li+]i, serum [Li+] ([Li+]e), Na+/Li+ exchange parameters, membrane phospholipid levels, [Mg2+]f, and Li+ membrane binding affinities. Comprehensive statistical analyses assessed correlations among the biochemical data. We used path analysis statistics to propose potential pathways in which the data were correlated.

RESULTS

We found significant correlations within the three Na+/Li+ exchange parameters and percentage composition of the membrane phospholipids. Additional correlations existed between [Mg2+]f and Vstd, Km, or phospholipid composition, between [Li+]i and percentage of phosphatidylcholine, and between percentage of phosphatidylserine and Km. Based on these findings, we hypothesized and statistically determined the most probable pathway through which these parameters were intercorrelated.

CONCLUSIONS

Significant correlations existed between the biochemical parameters that describe the cell membrane abnormality and the Li+/Mg2+ competition hypotheses. Using path analysis statistics, we identified a biochemical pathway by which Li+ may assert its cellular effects. This study serves as an illustrative example how path analysis is a valuable tool in determining the direction of a certain biochemical pathway.

Trace lithium in mood disorders

BACKGROUND

Variations in trace (endogenous) lithium exchanges have been postulated to play a role in the pathophysiology of affective diseases. This prospective study aimed to check whether plasma, erythrocytes and urine trace lithium levels were altered in mood disorders.

METHODS

Trace lithium was determined by atomic absorption spectrophotometry in patients without mood stabilizing drugs or somatic diseases, hospitalized for bipolar affective disorders, major depressive episodes, and other psychiatric disorders with depressive features. Patients admitted for psychotic disorders without mood alterations and healthy volunteers served as controls.

RESULTS

There were no differences in trace lithium status between the groups. Erythrocytes/plasma ratios appeared higher than described on therapeutic lithium (1.6+/-0.7, N = 199).

LIMITATIONS

The study had sufficient power to detect clinically significant differences in whole body lithium handling between the groups. However, it did not address alterations of lithium exchanges across neuronal membranes or the blood-brain barrier.

CONCLUSIONS

Alterations of membrane exchanges hypothetically associated with mood disorders are not reflected in plasma or erythrocytes trace lithium levels. The occurrence of mood disorders seems not to be related to abnormalities in endogenous lithium.

The lithium index in a one-year follow-up

1. In a one-year follow-up 191 patients on lithium therapy, besides their regular check-ups, were assessed on mood, side-effects and intracellular lithium. 2. The authors were not able to find a correlation between the so called lithium index (i.e. the quotient intracellular lithium/plasma lithium) and the mood score. 3. In the group of patients which used no co-medication at all during the year of the follow-up the authors also failed to find a correlation between the lithium index and some of the clinically most relevant side-effects. However, in that selected group of "only-lithium-using-patients"-only 29 in all-the authors found a remarkable stability in the index value. 4. So even if the authors, in fact, rejected the lithium index estimation as a tool in daily praxis, the authors would once again underline the interesting findings about the so-called lithium index.

Brain lithium concentration by 7Li- and 1H-magnetic resonance spectroscopy in bipolar disorder

A method was developed to measure lithium concentrations in the human brain using in vivo 7Li- and 1H-magnetic resonance spectroscopy (MRS). Lithium concentrations measured by MRS in 10 lithium-treated bipolar patients were at the half level of those measured in serum. Serial measurements indicated that lithium concentrations in the brain increased markedly during manic episodes, while serum concentrations were unchanged. These findings suggest that in vivo measurements of lithium concentrations in the brain, combined with measurements of concentrations in serum, may be useful in monitoring the effects of therapeutic drugs.

Rhythms and the pharmacology of lithium

Lithium is the treatment of choice for bipolar affective disorder (manic-depression) and is useful in other recurrent affective and nonaffective illnesses. This review discusses lithium's actions on period, phase, amplitude and coupling of biological rhythms that may relate to its therapeutic effectiveness. Alternatively, lithium might interact with environmental light to influence circadian rhythms by an action on the retina. The mechanisms responsible for lithium's chronopharmacological actions are not known, but cellular cations, phosphoinositide or adenylate cyclase second messenger systems, hormones and neurotransmitters may all be involved.

Measurement of tissue lithium concentration by lithium magnetic resonance spectroscopy in patients with bipolar disorder

Measurements of the lithium concentration in the occipital pole of the head and calf muscle of nine patients with bipolar disorder in remission were performed using in vivo lithium-7 nuclear magnetic resonance spectroscopy (7Li NMR). 7Li NMR measurements were performed on a 1-m-bore, 1.85-T, superconducting magnet supplemented with a multinuclear spectrometer, using 11.5-cm-diameter surface coils. The average lithium concentration in the occipital pole was 0.36 +/- 0.10 mEq/L, whereas in the muscle it was 0.50 +/- 0.17 mEq/L, both lower than the average serum lithium concentration (0.79 +/- 0.23 mEq/L). The average brain/serum lithium concentration ratio was 0.47 +/- 0.12 whereas the average muscle/serum lithium concentration ratio was 0.66 +/- 0.20. There was a positive correlation between the brain versus serum and brain versus muscle lithium concentrations. The hypothesis is advanced that the minimal effective concentration of brain lithium concentration for maintenance treatment of bipolar disorder is around 0.2-0.3 mEq/L.

Abnormalities of lithium transport across the erythrocyte membrane in depression and schizophrenia

Three mechanisms of lithium transport across erythrocyte membrane [lithium-sodium countertransport (LSC), lithium-potassium cotransport (LPC), and passive lithium diffusion (PLD)] were estimated in 27 acutely schizophrenic patients, 27 acutely depressed affective patients and in 18 control subjects. The activities of all mechanisms studied were significantly lower in both schizophrenic and depressed patients compared with controls. Analysis by gender showed that in control subjects, mean values of erythrocyte LSC and LPC were significantly higher in males compared with females. The decrease of LSC and LPC in depression and LSC in schizophrenia compared with control subjects was observed only in male patients but not in female ones. The results obtained suggest that lithium transport abnormalities during acute psychotic episodes are not specific to affective patients where lithium exerts its therapeutic action, but are also observed in schizophrenia. These abnormalities are more evident in male patients.

Measurement of lithium transport in RBC from psychiatric patients receiving lithium carbonate and normal individuals by 7Li NMR spectroscopy

A reproducible 7Li nuclear magnetic resonance (NMR) method, based on a modified inversion recovery (MIR) pulse sequence, was used to discriminate between intra- and extracellular lithium concentrations in red blood cell (RBC) suspensions. The rates of Na(+)-Li+ countertransport determined by the 7Li NMR method were significantly correlated with the measurements made by atomic absorption (AA) for 14 psychiatric patients receiving lithium carbonate (r = 0.937) and 14 normal individuals (r = 0.931). As expected, the rates of Na(+)-Li+ countertransport measured by MIR were significantly lower for the psychiatric patients receiving lithium carbonate than for normal individuals. The 7Li NMR method provides RBC Li+ countertransport information comparable to AA for psychiatric patients and normal individuals. A description of the advantages of the 7Li NMR method in contrast to the AA method, including the study of Li+ interactions with RBC components such as membrane proteins and anionic phospholipids, is included.

Discerning the latent structure of hypothetical psychosis proneness through admixture analysis

The application of psychometric procedures to a normal population sample to detect individuals with increased liability for schizophrenia is a useful methodological adjunct to the traditional genetic high-risk strategy. A necessary and reasonable step in the process of establishing the utility of a viable psychometric index of schizotypy is the formal investigation of the latent structure of psychometric values. The present study used admixture analysis to examine the distribution of scores on the Perceptual Aberration Scale (PAS), an objective measure of hypothetical psychosis-proneness, in a randomly ascertained sample of 18-year-old university students (n = 707). We applied parametric methods that assumed normally distributed component distributions; viewed in this context, our results are hypothesis-generating and not definitive confirmation of specific hypotheses. Within our methodological framework, the results provide strong evidence for the commingling of normal distributions, even after allowing for unequal variances across components and after removing skewness. The overall distribution of power-transformed data is consistent with the existence of three qualitatively distinct classes of PAS responders. We discuss our results in light of Meehl's model of schizotaxia, a "mixed model" of inheritance of liability to schizophrenia, and we review the methodological implications of our findings for future research.

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.

Psychometric deviance in offspring at risk for schizophrenia: II. Resolving heterogeneity through admixture analysis

The longitudinal and prospective study of offspring at risk for schizophrenia is complicated by within-group heterogeneity in liability, as only a subgroup of those at risk will ultimately become affected. Here, we attempt to resolve such heterogeneity in the New York High-Risk Project by conducting an admixture analysis of values on a psychometric index of liability to schizophrenia derived from the Minnesota Multiphasic Personality Inventory (MMPI). We fit mixtures of components to the overall distribution in 171 children from three criterion groups: offspring at risk (HR) for schizophrenia, psychiatric comparison (PC) offspring at risk for affective illness, and normal comparison (NC) offspring not at increased risk for psychiatric morbidity. The distribution of psychometric scores was bimodal, and separation of two latent classes showed that there is a valid and nonarbitrary distinction between a subgroup of MMPI-deviant (primarily HR) offspring and a larger homogeneous group of MMPI-nondeviant HR, PC, and NC subjects. While continued followup is required to demonstrate a correspondence between these two classes and an underlying taxonomy of liability to schizophrenia, our findings demonstrate the utility of objective psychometric measurement and admixture analysis for resolving within-group heterogeneity in high-risk research. The wider implications of including our MMPI indicators in other genetic investigations of schizophrenia are discussed.

Transmission of a psychometric indicator for liability to schizophrenia in normal families

The genetic analysis of schizophrenia would be facilitated by identification of a heritable correlate of liability. Deviance on an index of Minnesota Multiphasic Personality Inventory (MMPI) signs is associated with the disease phenotype; the familial aggregation and mode of transmission of this continuous psychometric indicator have yet to be established. In this paper, we examine the indicator through commingling analysis and segregation analysis with both the mixed and unified models on 65 nuclear families containing 211 normal individuals. Evidence for a high degree of familiality is found. Analysis of untransformed data under a conditional likelihood provides evidence for Mendelian transmission of a major gene with commingling of two distributions. The frequency of the "high index score" allele is 0.15, with the gene accounting for 31% of the total population variance; such a locus would be relevant to the study of psychopathology as 28% of the population would carry at least one deviant allele. When power-transformed scores are used to eliminate skewness, there is evidence for one distribution and it is not possible to distinguish single gene from multifactorial (polygenic or cultural) inheritance. While our findings regarding mode of transmission must be interpreted cautiously and confirmation of a single locus requires further study, demonstration of familiality warrants continued investigation of the index as an indicator of liability for schizophrenia.

Commingling and segregation analyses: comparison of results from a simulation study of a quantitative trait

Commingling analysis is commonly used to provide preliminary evidence for a single genetic locus with a major effect on the quantitative trait of interest. In this paper, the effectiveness of commingling analysis as a screening technique to identify samples for segregation analysis is assessed by applying both commingling and segregation analyses to samples of simulated pedigree data in which a major locus is segregating in the presence of polygenes and an individual-specific environmental effect. Under the circumstances simulated here, there is evidence for a single locus from segregation analysis but not from commingling analysis in at least 20% of the samples. No more than 2% of the samples provided evidence for commingling but not for segregation of a single locus. Comparisons of the samples that give evidence for both commingling and segregation, evidence for one but not the other, and no evidence for either show that evidence for commingling depends on the distributional characteristics of the trait in the sample, while support for the single locus from segregation analysis depends on both the distributional characteristics as well as the transmission of the rarer allele from parents to offspring. Since lack of commingling does not rule out the existence of a single locus in the realistic situations considered here, commingling analysis has limited usefulness as a screening technique for the presence for a single locus. In contrast, evidence for commingling does suggest the possibility that a single locus has a major effect on the trait and commingling analysis can provide guidance in the choice of initial parameter estimates for segregation analysis.

Method for prediction of serum lithium levels

A new computer-assisted method for predicting lithium levels and consulting dosage of lithium is demonstrated. The method is based on a mathematical model describing elimination of lithium after lithium treatment of any duration and regularity. From two values of serum concentration of lithium obtained during a single day, parameters of the model are computed and used for prediction. In an evaluation study involving 20 inpatients, the results demonstrated a high correlation between predicted and observed levels (r = 0.80) and revealed no systematic error of prediction. The elimination rate of lithium in these patients was unrelated to age or to duration of previous lithium therapy.

Kinetics of erythrocyte lithium-sodium countertransport in patients with affective illness before and during lithium therapy

Previous investigations have elucidated an erythrocyte lithium-sodium countertransport (LSC) system as the primary mechanism for extruding lithium from the cell, and this activity has been described in terms of Michaelis-Menten kinetics. In most clinical studies the maximum velocity (Vmax) of the LSC has been measured by estimating the rate of lithium efflux from lithium-loaded cells. To date, few studies have examined whether the affinity (Km) of the LSC for lithium might be altered in patients with affective disorders. In the present study we examined LSC kinetic parameters (Vmax, leak, Km, and in vitro lithium ratio) at baseline in 80 patients with affective disorder and 25 healthy control subjects, and after 6 weeks of lithium administration in 33 of the patients. No differences in Vmax were observed between any patient and control group, although Vmax was significantly lower in unipolar depressed men compared to bipolar men (P = 0.043). The affinity (Km) of the transport 'carrier' for lithium did not differentiate between patient and control groups. Chronic lithium administration caused a decreased Vmax in bipolar men (P = 0.015), an increase in the in vitro lithium ratio in bipolar men (P = 0.002) and bipolar women (P = 0.002), and a marginal increase in Km in bipolar men (P = 0.08) and bipolar women (P = 0.06). Although the present data do not demonstrate an underlying difference for Km between affectively ill patients and controls, they do indicate a decrease in the affinity of the transport 'carrier' for lithium after chronic lithium administration.

Genetic studies of cation tests and hypertension

Several tests of cation concentration and transport are being studied among members of large Utah pedigrees as part of a study of the genetic and environmental determinants of essential hypertension. Corrected urinary sodium excretion and plasma sodium concentration correlated well in spouses and siblings (r = 0.21-0.54, p less than 0.001), suggesting the effects of shared family environment (e.g., sodium intake). Intraerythrocytic sodium concentration and sodium-lithium countertransport showed no significant correlation in spouses and very significant correlations between siblings and between parents and offspring (r = 0.34-0.58, p less than 0.001), suggesting mostly genetic determination. Using maximum likelihood tests of different genetic models, both sodium-lithium countertransport and intraerythrocytic sodium showed predominantly polygenic determination (H2 = 70%) and some possible major gene determinants (H2 = 18-25%) for a total heritability of 89 to 95% for these characteristics. These data suggest both genes and shared family environment contribute to the familiality of cation tests. They also illustrate the need and utility of quantitative methods for objective analysis of pedigree data.

A review of the biochemical and neuropharmacological actions of lithium

The pharmacological actions central to the therapeutic effects of lithium have not yet been established, despite almost 40 years of clinical use and scientific investigation. We review the biochemical and neuropharmacological data relating to this problem and attempt to identify profitable areas for further research.

Lithium ratio in vitro: familial patterns of illness

Psychiatric illness in first-degree relatives of psychotic patients with low, intermediate, and high red blood cell (RBC) in vitro lithium ratio (LR) was investigated using the Schedule for Affective Disorders and Schizophrenia and DSM-III. Fewer schizophrenic spectrum disorders were found in the first-degree relatives of high and low LR probands as compared to intermediate LR probands; high LR psychotic probands had families with an increased frequency of depressive spectrum disorder. Alcohol dependence and abuse was particularly prominent in the first-degree relatives of the higher LR probands. High LR may identify a disease that does not belong to the familial-genetic disorders of the schizophrenic spectrum; this illness may bear a closer relationship to disorders of the depressive spectrum.

Lithium prophylaxis of recurrent affective disorders

The mode of action of lithium is reviewed in the light of advances in the understanding of calcium channelling and calmodulin-activated Ca ATPase. The relevance to changes in receptor sensitivity is discussed.

Effects of phenothiazine treatment on the physical properties of platelet membranes from psychiatric patients

Exposure of normal platelet membranes in vitro to clinically relevant concentrations of phenothiazines has been reported to result in an increase in the structural order of the hydrocarbon region of these membranes (Zubenko and Cohen 1984b,c). In this study, the order parameters (reciprocal of fluidity) of platelet membranes prepared from psychiatric patients receiving phenothiazine antipsychotic drugs were compared to those of an otherwise matched population of psychiatric patients who were not receiving medications that significantly affect this cell membrane property in vitro (Zubenko and Cohen 1984b,c). Membrane order was determined ex vivo by steady-state fluorescence polarization measurements employing 1,6-diphenyl 1,3,5-hexatriene, a fluorescent probe that localizes preferentially in the hydrocarbon region of cell membranes. Phenothiazine administration was associated with a significant increase in platelet membrane order and most likely results from a direct action of these agents on cell membranes. The platelet membrane order parameters of phenothiazine-free patients did not differ significantly from those of a matched group of unmedicated, normal controls. Platelet membrane order was not correlated with daily phenothiazine dose or serum cholesterol concentration. Patient gender did not significantly affect platelet membrane order in any of the groups studied. The potential physiological and clinical significance of phenothiazine-induced increases in cell membrane order is discussed.

Lithium therapy for mania and depression

The literature on lithium carbonate was reviewed for clues to the processes involved in mania. Lithium has proved effective therapeutically and prophylactically for mania and depressive disorders. Children and adolescents as well as adults tolerate lithium well. Side effects rarely are serious enough to necessitate having lithium therapy. Some success with schizophrenia and schizoaffective disorders has broadened the scope of lithium's therapeutic efficacy but also blunted the expectation for a direct relationship between lithium and the processes involved in mania. Research points to neurotransmitters as contributing to the etiology and symptom pattern of mania.

Effects of psychotropic agents on the physical properties of platelet membranes in vitro

Normal platelet membranes were exposed in vitro to a variety of psychotropic medications commonly used in the treatment of patients with psychiatric disorders. Changes in structural order at the hydrocarbon region of the drug-exposed membranes were determined by steady-state fluorescence polarization measurements employing the fluorescent probe 1,6-diphenyl-1,3,5-hexatriene (DPH). Chlorpromazine, an aliphatic phenothiazine, produced a significant increase in DPH fluorescence polarization at concentrations from 2-200 microM. Thioridazine, a piperidine phenothiazine, and three piperazine derivatives, perphenazine, trifluoperazine, and fluphenazine, produced significant increases in this parameter at concentrations from 20-200 microM. The other agents tested, including thiothixene, lithium, antidepressants, anxiolytics, and anticonvulsants, were without effect in the concentration ranges examined. The phenothiazine-induced increase in DPH fluorescence polarization apparently depended on the structure of the phenothiazine nucleus; changes in side-chain structure appeared to modulate this effect, most likely by altering the inherent membrane solubility of the agents.

Interdependency of lithium ratio, plasma lithium level and clinical state in patients with affective disorders

The interrelationship between lithium ratio, lithium plasma level and the different clinical phases of 31 patients with bipolar affective disorder has been investigated. the interdependency of these variables was followed longitudinally during different phases of the illness while under lithium therapy. Although positive correlations between lithium ratio and lithium plasma levels were evident, the lithium ratio values in the euthymic group were significantly higher than those in the manic and depressive groups, independently of the plasma lithium level. Our data suggested that RBC/plasma lithium ratio might be a sensitive state dependent index in affective bipolar illness.

Beta-adrenoceptor binding defects in cell lines from families with manic-depressive disorder

Binding of 125I-iodohydroxybenzylpindolol to beta-adrenoceptors has been examined in lymphoblastoid cell lines from members of 5 families affected by manic-depressive disorder. Cell lines from 6 manic-depressives, 7 unaffected relatives and 11 non-psychiatric controls were examined. Binding was reduced to less than half of control values in cell lines from 4 out of 6 manic-depressives and only 1 out of 18 unaffected relatives or controls. All the cell lines with reduced beta-adrenoceptor binding came from 3 families; members of the remaining 2 families showed normal binding. These findings suggest that genetic heterogeneity is present in manic-depressive disorder and that a beta-adrenoceptor defect may influence genetic susceptibility to the disorder.

In vitro effects of psychotropic agents on the microviscosity of platelet membranes

Normal platelet membranes were exposed in vitro to a variety of psychotropic agents, including chlorpromazine, fluphenazine, haloperidol, imipramine, and lithium. Changes in microviscosity of the hydrocarbon layer of the drug-exposed membranes were determined by steady-state fluorescence polarization measurements, employing the fluorescent probe 1,6-diphenyl 1,3,5-hexatriene (DPH). Concentrations of the phenothiazines chlorpromazine and fluphenazine above 200 nM produced significant increases in microviscosity, while haloperidol produced a small but consistent decrease in microviscosity in the concentration range of 200 nM to 200 microM. Imipramine and lithium were without effect. The phenothiazine-induced increase in microviscosity was apparently dependent upon the structure of the phenothiazine nucleus; side chain structure was less important to this effect.

Lithium transport in red cells of patients with affective disorders

Variation in red cell Li+ transport as mediated by the Li+-Na+ exchange pathway (Li+-Na+ counterflow) appears to cause wide variation between psychiatric patients in the Li+ ratio (erythrocyte/plasma) in vivo during Li+ treatment. We obtained significant correlations between Li+ ratios determined in vivo and several measures of Li+ transport as mediated by Li+-Na+ exchange. Patients with bipolar illness had significantly lower rates of Li+ transport as mediated by this pathway than did normal subjects.

Sodium-dependent lithium ion efflux from murine neuroblastoma and rat glioma cells: a minor pathway for efflux of lithium ions

Lithium ion efflux by murine neuroblastoma (clone N1E-115) and rat glioma (clone C6) cells was studied to determine the presence of a phloretin-sensitive sodium-lithium countertransport pathway which has been found in human erythrocytes. Although this pathway could be identified in these cultured cells, unlike that in red blood cells, it was a very minor (less than 20%) component of the overall efflux of lithium ions from these cells of nervous tissue origin.

Blood cells as biological trait markers in affective disorders

Data are reviewed on platelet monoamine oxidase activity, red blood cell/plasma lithium ratio, and tritiated imipramine binding to platelet membranes as trait markers for affective disorders. The results of various studies are not in agreement. Differences in methodological procedure are probably central to such discrepancies. At the present time, no single biological abnormality of blood cells has proved to be a trait marker for affective disorders; thus their use to identify vulnerability to mood disorders or predict favourable response to pharmacological treatment appears to be premature.