Abnormal lithium and sodium transport in erythrocytes of a manic patient and some members of his family

Identification of Li+ binding sites and the effect of Li+ treatment on phospholipid composition in human neuroblastoma cells: a 7Li and 31P NMR study

Li(+) binding in subcellular fractions of human neuroblastoma SH-SY 5 Y cells was investigated using (7)Li NMR spin-lattice (T(1)) and spin-spin (T(2)) relaxation measurements, as the T(1)/T(2) ratio is a sensitive parameter of Li(+) binding. The majority of Li(+) binding occurred in the plasma membrane, microsomes, and nuclear membrane fractions as demonstrated by the Li(+) binding constants and the values of the T(1)/T(2) ratios, which were drastically larger than those observed in the cytosol, nuclei, and mitochondria. We also investigated by (31)P NMR spectroscopy the effects of chronic Li(+) treatment for 4--6 weeks on the phospholipid composition of the plasma membrane and the cell homogenate and found that the levels of phosphatidylinositol and phosphatidylserine were significantly increased and decreased, respectively, in both fractions. From these observations, we propose that Li(+) binding occurs predominantly to membrane domains, and that chronic Li(+) treatment alters the phospholipid composition at these membrane sites. These findings support those from clinical studies that have indicated that Li(+) treatment of bipolar patients results in irregularities in Li(+) binding and phospholipid metabolism. Implications of our observations on putative mechanisms of Li(+) action, including the cell membrane abnormality, the inositol depletion and the G-protein hypotheses, are discussed.

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.

Erythrocyte membrane structure in bipolar affective disorder: a non-replication

Fifteen bipolar patients were compared with sixteen controls in an attempt to replicate the findings of Pettegrew et al. in 1982 of decreased fluidity in the hydrocarbon core of the erythrocyte membrane. No significant differences were seen between groups. The present control group shows very similar membrane characteristics to the original control series; however, the bipolar patient group is not similar. Possible explanations are discussed.

Membrane properties of erythrocytes in subjects undergoing multiple blood donations with or without recombinant erythropoietin

To examine the characteristics of 'young' human red cells, we studied blood from seven healthy male volunteers who developed systemic reticulocytosis during a 3-week blood donation period. Each of these subjects donated a total of 6 units (450 ml/unit) of blood (2 units/week for 3 weeks) with subcutaneous recombinant erythropoietin (SC rEPO; 200 U/kg daily for 3 weeks). Two of these subjects were also studied with a similar protocol in the absence of rEPO (4.5 +/- 0.5 units donated). SC rEPO administration was associated with an increased K content of the erythrocyte and with the appearance of hypochromic cells, which were initially normocytic and then became normochromic and microcytic. Measurements of cation transport revealed that, with the exception of the Na-K-Cl cotransport, all the systems studied increased their activities following blood donations with or without SC rEPO. The increase was highest in the K-Cl cotransport (2- and 5-fold for control and rEPO parts of the study, respectively), while the Na-K pump increased slightly in control and 40% with rEPO. The Na-Li countertransport increased 40% and 100% in the control and rEPO parts of the study, respectively. Concomitant with increased ion transport activity, electron microscopic studies of plasma and red cells of subjects receiving SC rEPO showed the presence of circulating exosomes and cytoplasmic multivesicular bodies. The transferrin receptor was detected in the circulating exosomes, thereby providing evidence that, as do nonhuman red cells, maturing human reticulocytes shed exosome-associated transferrin receptors.

Lithium transport in human fibroblasts: relationship to RBC lithium transport and psychiatric diagnoses

Cultured fibroblasts were prepared from six normal controls, five DSM-III manic patients, and six DSM-III schizophrenic patients. Lithium (Li+) uptake, 24-hour Li+ ratios, and steady-state membrane potential were measured in these cell lines. The uptake of 10 mM Li+ reached maximum at 2 hours, with an intracellular concentration of approximately 15 mM. No significant difference in uptake was found among subject groups. Twenty-four hour Li+ (ratio of intracellular/extracellular Li+) ratios were determined by incubating the cell lines for 24 hours in the presence of 2 mM Li+. No significant difference was observed among groups; nor was there any significant correlation between the fibroblast 24-hour ratios and 24-hour in vitro ratios determined in donor red cells. The relationship between membrane potential and the 24 hour Li+ ratio in fibroblasts was determined. The average potential in these cell lines was -56 mV and was not affected by Li+ treatment. No correlation between the Li+ ratio and membrane potential was found.

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.

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.

Management of hypertension in high school students by using new salt titrator tape

In a blood pressure screening program involving 6589 high school students, 180 male (4.7%) and 17 female (0.6%) students were identified as borderline hypertensive. The 174 hypertensive male adolescents studied further showed pathophysiological features such as a significantly higher frequency of obesity, higher 24-hour urinary sodium excretion, higher hematocrit value, higher sodium and lower potassium concentration in red blood cells, and higher ouabain-sensitive sodium efflux compared with the control group (231 male students; p less than 0.05). When used alone, the ordinary 10-week period of counseling about a low salt diet failed to significantly reduce the blood pressure of hypertensive students. However, when education and counseling efforts were combined with self-monitoring of salt (chloride) excretion in overnight urine samples using a new salt titrator tape developed in our laboratory, 24-hour urinary sodium excretion, weight, and blood pressure decreased significantly over 10 weeks (mean reduction: 52 mEq/day for 24-hour urinary sodium excretion, 1.7 kg for weight, 12/7 mm Hg for blood pressure). These results indicate that blood pressure of borderline hypertensive adolescents could be effectively reduced with this nonpharmacological method of dietary education. Such systematic management might be of importance for the prevention of essential hypertension.

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 distribution in the brain of normal mice and of "quaking" dysmyelinating mutants

Using nuclear reaction 6Li(n, alpha)3H and dielectric detectors, we have studied the distribution of Li in the brain of adult mice, following Li treatment of the animals. Two strains of animals were used in parallel: "quaking" dysmyelinating mutants and normally myelinated controls. The distribution appeared to be sharply regionalized in the brain of the normal mice (higher Li concentration in the gray rather than in the white matter, with the area postrema being particularly Li rich). In contrast, the Li distribution was practically homogeneous in the brain of the quaking dysmyelinating mutants, with a mean Li concentration comparable to that in the gray matter of the controls. The present method of Li detection has made it possible to estimate the Li equilibrium potentials (nerve cells with regard to plasma) in the different brain substructures. The results are consistent with (a) Li being actively extruded from nerve cells in all the cases and (b) myelination decreasing the relative importance of the passive component of Li transport in the nerve cells, as compared with the active component.

Inhibitin: a specific inhibitor of sodium/sodium exchange in erythrocytes

An inhibitor of ouabain-insensitive sodium/sodium exchange in erythrocytes has been isolated from leukemic promyelocytes. To explore the specific effects of this inhibitor, named inhibitin, sodium transport experiments were carried out in human erythrocytes. Inhibitin reduced ouabain-insensitive bidirectional sodium transport. It did not change net sodium fluxes, had no significant effect on rubidium influx, and did not inhibit sodium-potassium-ATPase activity. The inhibitory effect of inhibitin was studied on sodium/sodium exchange and on sodium/lithium countertransport in 140 mM sodium and in sodium-free media. In the presence of sodium, inhibitin reduced sodium and lithium efflux to that observed in sodium-free medium. Inhibitin showed no reduction in sodium or lithium efflux when sodium was replaced by choline chloride or Mg2+. When inhibitin was combined with one or more of the other transport inhibitors (i.e., ouabain, furosemide, or bumetanide and amiloride), its inhibitable component remained distinct and it did not overlap with that of the other inhibitors. These studies show that inhibitin is a specific inhibitor of carrier-mediated sodium/sodium exchange and sodium/lithium countertransport processes in human erythrocytes.

Absence of significant sodium-hydrogen exchange by rabbit erythrocyte sodium-lithium countertransporter

Red blood cells of several mammalian species (e.g., human, rabbit, bovine) possess a countertransport system for Li and Na. We have used rabbit red blood cells to determine the extent of sodium-proton exchange by this countertransporter. Ouabain-insensitive 22Na efflux into phosphate-buffered K-acetate media of varying Na concentrations was determined at extracellular pH 7.5 and 6.9. To maintain the intracellular pH at approximately 7.2, most of the acetate in the pH 6.9 medium was replaced by gluconate, a nonpenetrating anion. Extracellular Na strongly (greater than 10-fold) stimulated the 22Na efflux in both high- and low-pH media, but the K1/2 for this stimulation was higher at pH 6.9. This is consistent with a competitive binding of H to the outward-facing transport site. However, the lower pH itself, in a Na-free medium, stimulated the 22Na efflux only very slightly. The 22Na efflux stimulated by lowering the extracellular pH to 6.9 was less than 1% of the stimulation produced by 100 mM extracellular Na. It is concluded that, although H appears to bind to the substrate site of the Na-Li exchanger, there is no significant H transport in the physiological pH range.

Erythrocyte lithium efflux in bipolar patients and control subjects: the question of reproducibility

The reproducibility of in vitro erythrocyte lithium efflux and lithium efflux in the presence of selected membrane transport inhibitors (phloretin, ouabain, 4,4'-diisothiocyano-2,2'-disulphonic acid stilbene, and p-chloromercury-benzene sulphonate) was investigated in bipolar patients and age- and sex-matched control subjects. Efflux experiments were repeated three times in each patient-control pair within a period of 14 days. No differences were detected between patients and control subjects in any of the parameters measured. All components of lithium efflux showed wide day-to-day variation in the same subject in both patients and control subjects. Intersubject variability, however, was significantly greater than intrasubject variation. Since intraindividual variation of phloretin-inhibited lithium efflux was found to be considerable, and no real patient-control differences could be detected, the significance of this in vitro parameter in bipolar affective illness seems somewhat questionable and should be carefully reconsidered. The relevance of these findings to the putative cell membrane dysfunction in this disease is discussed.

Anesthetic management of lithium-treated patients

In order to establish a protocol for the anesthetic management of patients undergoing lithium therapy, one must consider the mechanisms of lithium action. Many proposals for different mechanisms appear in the literature which attempt to explain the pharmacology, physiology, metabolism, administration, dosage and adverse effects of lithium. This paper reviews the pertinent scientific and clinical information to enable the anesthesiologist to rationally administer anesthesia to patients on a lithium regimen.

Genetic analysis of sodium-lithium countertransport in 10 hypertension-prone kindreds

The rate of sodium-lithium countertransport (SLC flux) across red cell membranes has been reported to be elevated in hypertensive persons and their relatives as compared to normotensive individuals without family histories of hypertension. We have investigated the inheritance of this trait in 434 persons from 10 kindreds. Relatives show positive correlation of SLC flux values, but there is no spouse-spouse correlation. Pedigree analysis favors a model of polygenic inheritance over models of major-gene inheritance. Major-gene index statistics and offspring-between-parent statistics provide similar results. The proportion of total phenotypic variance that is attributable to polygenic differences between persons is estimated at 71%. The SLC flux values of hypertensive persons in this study population are lower than those reported from Boston, but are similar to those reported from Europe. We found a broad overlap of SLC flux values for hypertensive and normotensive persons. We conclude that SLC flux probably is not useful as a preclinical marker for essential hypertension.

Membrane abnormalities in the psychoses and affective disorders

Erythrocyte ghost phospholipid data were collected on 67 psychotic and/or manic patients and compared to a group of 35 age and sex matched controls. Patients meeting DSM-III criteria for schizophreniform disorder or schizophrenia but not mania showed a small but significant decrease in membrane phosphatidylcholine (PC). In 53 of the patients data were available on lithium transport across red cell membranes. Patients in the upper quartile of the PC distribution showed a significant (-47%) decrease in the 24 h in vitro lithium ratio as compared to patients in the lower PC quartile. This difference was due to an increase in Na-Li+ counterflow activity in the upper PC quartile and not to a change in passive lithium leak. These data illustrate one example of a possible relationship between membrane composition and a membrane function, counterflow activity, which has been associated with the underlying mechanism(s) of lithium action.

Lithium, sodium and potassium transport in erythrocytes of manic-depressive patients

Different Li, Na and K transport pathways were assessed in erythrocytes from manic-depressive patients. No alteration in the Li-Na countertransport, Na,K cotransport or passive permeabilities was observed in either unipolar or bipolar manic-depressive patients. In addition, acute or chronic lithium treatment did not alter the maximal velocity of either the Li-Na countertransport or the Na,K cotransport. A two-fold reduction of the ouabain-sensitive Na efflux was observed among manic-depressive patients without alteration in the affinity of the Na pump for internal Na.

Lithium ratio in psychiatric patients: a caveat

We divided bipolar patient samples into two groups: Group I (off lithium 10 days to 2 weeks, n = 14) and group II (off lithium 3 weeks or longer, n = 13). Only group I was significantly different from controls. The mean for group II was significantly different from that for group I but not that for controls. Previous reports may have exaggerated the number of "high ratio" patients due to a treatment artifact. We recommend that patients be tested only after having been withdrawn from lithium treatment for 3 weeks or more. Otherwise spurious differences between patients and controls may result.

Lithium-sodium countertransport in erythrocytes of normal and hypertensive subjects. Relationship with age and plasma renin activity

Lii-Nao countertransport was measured in red blood cells of 58 normotensive subjects (27 females and 31 males), 60 patients with essential hypertension (26 females and 34 males), and in 28 with secondary hypertension (19 females and 9 males). The mean values (+/- SEM) expressed as mmol Li (1 red cells X hr)-1 were 0.18 +/- 0.02 (females) and 0.20 +/- 0.01 (males) in the control group, 0.34 +/- 0.04 (females) and 0.39 +/- 0.03 (males) in essential hypertension, 0.16 +/- 0.03 (females) and 0.19 +/- 0.02 (males) in secondary hypertension. The mean value of Lii-Nao countertransport obtained in essential hypertension was statistically different from those obtained in both normals (p less than 0.001) and patients with secondary hypertension (p less than 0.001). A negative correlation was found between age and Lii-Nao countertransport in normotensive males (r = - 0.648; p less than 0.001) but neither in normal females nor in patients with essential hypertension. A positive correlation (r = + 0.425; p less than 0.05) was found between plasma renin activity after intravenous furosemide and Lii-Nao countertransport in essential hypertension. These findings support the hypothesis of a characteristic cation transport across the red blood cell membrane of patient with essential hypertension which might be correlated with the plasma renin activity.

Essential hypertension: sodium-lithium countertransport in erythrocytes from patients and from children having one hypertensive parent

This report deals with the possibility that there is a specific change of the lithium transport across the membrane of erythrocytes from patients with essential hypertension. Sodium-lithium countertransport was significantly increased (p less than 0.005) in erythrocytes from 17 males with essential hypertension (mean 0.7 mmole (liter cells X hr)-1, range 0.4-1.6) compared to a group of 16 normotensive males (mean, 0.4 mmole (liter cells X hr)-1, range 0.3-0.6). A considerable overlap between the values from patients and controls was found. No significant increase of the transport function was found in a group of 14 female patients (mean 0.4 mmole (liter cells X hr)-1, range 0.2-0.6) compared with 10 normotensive female controls (mean 0.3 mmole (liter c hr)-1, range 0.3-0.6). A considerable overlap between the values from patients and controls was found. No significant increase of the transport function was found in a group of 14 female patients (mean 0.4 mmole (liter cells X hr)-1, range 0.2-0.6) compared with 10 normotensive female controls (mean 0.3 mmole (liter c hr)-1, range 0.3-0.6). A considerable overlap between the values from patients and controls was found. No significant increase of the transport function was found in a group of 14 female patients (mean 0.4 mmole (liter cells X hr)-1, range 0.2-0.6) compared with 10 normotensive female controls (mean 0.3 mmole (liter cells X hr)-1, range 0.1-0.6). Determination of sodium-lithium countertransport in red blood cells from nine children with and 14 without known familial disposition for essential hypertension did not demonstrate a close coupling between genetic disposition and the membrane transport function. In spite of the very small intraindividual variability of the transport function, studies of changes in sodium-lithium counter-transport are hampered by considerable interindividual variability of the transport in red cells from apparently normal individuals.

Pharmacological and electrophysiological characterization of lithium ion flux through the action potential sodium channel in neuroblastoma X glioma hybrid cells

Interaction of Li+ with the voltage-dependent Na+ channel has been analyzed in neuroblastoma X glioma hybrid cells. The cells were able to generate action potentials in media containing Li+ instead of Na+. The uptake of Li+ into the hybrid cells was investigated for the pharmacological analysis of Li+ permeation through voltage-dependent Na+ channels. Veratridine and aconitine increased the uptake of Li+ to the same degree (EC50 30 microM). This increase was blocked by tetrodotoxin (IC50 20 nM). Veratridine and aconitine did not act synergistically; however, the veratridine-stimulated influx was further enhanced by the toxin of the scorpion Leiurus quinquestriatus (EC50 0.06 micrograms/ml). This stimulation was also blocked by tetrodotoxin. Thus, the voltage-dependent Na+ channel of the hybrid cells accepts both Li+ and Na+ in a similar manner.

Outward sodium and potassium cotransport in human red cells

This paper reports some kinetic properties of Na-K cotransport in human red cells. All fluxes were measured in the presence of 10(-4) M ouabain. We measured Na and K efflux from cells loaded by the PCMBS method to contain different concentrations of these ions into a medium that contained neither Na nor K (MgCl2-sucrose substitution) in the absence and presence of furosemide. Furosemide inhibited 30-60% of the total efflux depending on the internal ion concentration and the individual subject. We took the furosemide-sensitive fluxes to be a measure of Na-K cotransport. The ratio of Na to K cotransport was 1 over the entire range of internal Na and K concentrations studied. When Na was substituted for K as the only internal cation, cotransport was maximally activated when the Na and K concentrations were between 20 and 90 mmol/liter cells. The concentration of internal Na required to produce half-maximal cotransport was about 13 +/- 4 mmol/liter cells (n = 4), while the comparable concentration of K was somewhat lower. The activation curve was definitely sigmoid in character, suggesting that at least two Na ions are involved in the transport process. The maximum of Na-K cotransport was about 0.5 +/- 0.15 mmol/liter cells x hr (n = 5); it had a flat maximum in the medium at about pH 7.0, decreasing in both the acid and alkaline sides. Furosemide-resistant effluxes were found to be linear functions of internal Na and K concentrations and to yield rate coefficients of 0.019 +/- 0.002 hr-1 and 0.014 +/- 0.002 hr-1 (n=7), respectively. These values are of the same order of magnitude expected of ions moving across phospholipid bilayers.

The activity of the lithium--sodium countertransport system in erythrocytes in depression and mania

The activity of the lithium--sodium countertransport system in erythrocytes was estimated in 16 control subjects and 28 patients suffering from affective disorders (11 bipolar, 17 unipolar) during depression, mania and remission. In all the patients studied, mean estimates of countertransport were significantly lower during an episode than after remission, with low values occurring more frequently in mania than in depression in bipolar patients. The mean values in patients with affective disorders but who were in remission remained lower than those of control subjects. Lowest values occurred more frequently in patients with bipolar than in those with unipolar illness. the possible physiological significance of reductions in the activity of the lithium--sodium countertransport mechanism in red cells was discussed.

Distinguishing homozygous and heterozygous cystic fibrosis fibroblasts from normal cells by differences in sodium transport

We have found that cultured fibroblasts from patients with cystic fibrosis (CF) accumulate less 22Na in the presence of ouabain than do normal cells. After equilibration with 22Na in ouabain-exposed cells to that in unexposed cells, after five hours of incubation, was 2.34 +/- 0.14 (mean +/- S.D.) in 13 fibroblast strains from normal subjects and 1.33 +/- 0.08 in eight strains from patients with CF. Cells from eight different obligate CF heterozygotes (parents of children with CF) had a ratio of 1.38 +/- 0.07; those from three unaffected siblings (who have a two-thirds chance of carrying the disease) had a ratio of 1.27 +/- 0.04. The differences between CF homozygotes or heterozygotes and normal subjects were highly significant (P < 0.001), but there was considerable overlap between CF homozygotes and heterozygotes. This abnormality of sodium transport provides an unequivocal in vitro test that distinguishes normal cells from cells derived from CF homozygotes or heterozygotes. It should be useful for the identification of carriers of the CF gene.

Alteration of erythrocyte phosphate transport in primary depressive disorders

Plasma and erythrocyte phosphate levels, concentrations of red cell organic phosphate ester fractions (acid labile and acid resistant phosphate pools) and intracellular ATP content were determined in 16 patients with bipolar depression, in 14 subjects with unipolar depression as a group of primary affective disorders, in 15 patients suffering from neurotic depression and in 45 healthy controls. Simultaneous in vitro measurements were carried out to detect the exchange rates of inorganic phosphate between the extracellular phosphate pool and the different intracellular phosphate fractions, by use of 32P and applying tracer kinetic analysis. Plasma and red cell inorganic phosphate levels, passive phosphate transport and transfer of inorganic phosphate into the membrane ATP pool were significantly lowered in the primary depressive group as compared to the biochemical values observed in the neurotic group and in the healthy controls. The results suggest an alteration in anion transport across the red cell membrane in primary depressive disorders.

Reassessing the bipolar-unipolar dichotomy

This paper is a critical review of the literature on the dichotomous classification of affective disorders into unipolar and bipolar types. The majority of genetic studies show significant overlap in the liability to develop two forms of illness, and the majority of lithium studies show a similar clinical responsiveness of both groups to both acute and maintenance treatment. Biological studies comparing the two groups are difficult to interpret as most have compared manics to depressives without controlling for motor activity, excitement, and other state-dependent clinical variables. Viewed in light of our research findings in a recent genetic study of affective states, we believe these data suggest that the separation of affective disorders by polarity may have been premature, and that the search for heterogeneity should now be carried out using alternative strategies.

Activity of erythrocyte Na,K-ATPase in manic patients

Erythrocyte membrane Na,K-ATPase activity of manic patients was studied. The activity of patients in acute manic phase was higher than that of normal controls, while that of patients in normal phase was not. Even in the same patient, the activity in acute phase was higher than that in normal phase. Mg-ATPase activities did not differ between controls and patients. These findings clearly indicate a possible correlation between change in clinical phase in manic patients and change of erythrocyte membrane Na,K-ATPase activity.

Increased sodium-lithium countertransport in red cells of patients with essential hypertension

This paper describes experiments showing that one of the pathways of sodium transport across the red-cell membrane, sodium-lithium countertransport, is faster in patients with essential hypertension than in control subjects. This transport system accepts only sodium or lithium and is not inhibited by ouabain. The maximum rate of transport shows inherited differences. The mean maximum rate of sodium-lithium countertransport was found to be 0.55 +/- 0.02 (mean +/- S.E.M.) mmol (liter of red cells X hour)(-1) in a group of 36 patients with essential hypertension and 0.24 +/- 0.02 in 26 control subjects (P less than 0.001). The first-degree relatives of eight patients with essential hypertension and 10 control subjects had mean maximum rates of sodium-lithium countertransport of 0.54 +/- 0.05 and 0.23 +/- 0.02, respectively. Five patients with secondary hypertension had normal mean maximum rates of sodium-lithium countertransport. The relation between heritability of red-cell sodium-lithium countertransport and essential hypertension should be investigated further.

Transmembrane distribution of lithium and sodium in erythrocytes of depressed patients

In this investigation the intracellular: extracellular distribution of lithium across the erythrocyte membrane (RBC lithium distribution) was studied in vitro and in vivo. The in vitro studies were conducted by incubating cells from drug-free subjects in lithium-containing physiologic media. The in vivo studies consisted of measurements of plasma and erythrocyte (RBC) lithium and sodium concentrations during lithium carbonate treatment. Previous observations of a correlation between in vitro and in vivo RBC lithium distribution values were verified, and it was found that addition of 0.1 mM ouabain to the in vitro incubation media abolished this correlation. To examine the relationship between RBC lithium distribution and specific clinical features of depression, in vitro studies were conducted with RBCs from 20 depressed patients and 14 nondepressed control subjects. The patients were categorized as having bipolar (manic-depressive), unipolar, or secondary depressive disorders. After in vitro incubation with lithium for 48 h, the RBCs from bipolar patients had lithium distribution values that were similar to those observed in ouabain-treated cells. It appears that the lithium transport characteristics of RBCs of bipolar patients may differ from those of other depressed patients or nondepressed subjects.

The influence of external sodium and potassium on lithium uptake by primary brain cell cultures at "therapeutic" lithium concentration

The ionic regulating of lithium homeostasis and steady-state intra:extracellular lithium distribution in the brain can be approached by experimental methods using intact nerve cells in vitro. Primary cultures prepared from chick embryonic brain were applied to study the effect of extracellular sodium and potassium on the lithium uptake of nerve cells at 'therapeutic' lithium concentration (1.5 mM). Lithium influx and the level of steady-state intracellular lithium were significantly reduced by increasing the external sodium concentration. At physiological extracellular sodium level, the steady-state content of lithium in the brain cells was about half of that observed in the presence of 10 mM sodium in the incubation media and the value of the intra:extracellular lithium distribution ratio was below 1. External potassium (0.5 - 3mM) strongly inhibited lithium uptake of the nerve cells. Ouabain (10(-4)M) had no effect on this potassium-sensitive lithium uptake in Tyrode media. Sodium influx studied by isotope tracer methodology was higher in cultures preloaded with lithium as compared to that of the controls. It can be concluded that sodium and potassium ions, at physiological concentrations, significantly influence lithium uptake as well as the intra:extracellular lithium distribution in brain cell cultures.

Sodium-dependent lithium efflux from red cells in affective disorders

Steady state red blood cell/plasma lithium concentration ratios were determined simultaneously with the in vitro sodium-dependent downhill lithium efflux from red cells during maintenance lithium treatment in 22 bipolar depressed patients, 17 unipolar depressed patients, and 28 psychiatric control patients. The values of the sodium-dependent lithium efflux were significantly correlated with the steady-state lithium levels in red blood cells and plasma. A profound difference in sodium-dependent lithium efflux from red cells was found between controls and bipolar patients and to a lesser degree between controls and unipolar patients.

Chronic treatment with lithium or desipramine alters discharge frequency and norepinephrine responsiveness of cerebellar Purkinje cells

Cerebellar Purkinje cells were studied by electrophysiological techniques in rats treated chronically with either desipramine (DMI) or lithium chloride given intragastrically. A striking decrement occurred in discharge frequencies of simple spikes and climbing fiber bursts in both groups of animals, similar to the depression produced by iontophoresis of these agents. Chronic treatment with DMI markedly decreased responsiveness to iontophoretically applied norepinephrine (NE), whereas long-term LiCl therapy slightly enhanced response to NE; responses to gamma-aminobutyric acid were unchanged by these treatments. The inhibitory responses to locus ceruleus stimulation were unaffected by chronic LiCl treatment. The effects of these chronic treatments on responsiveness to NE are opposite to the effects these same drugs produce when administered by acute iontophoresis to single cells: DMI then potentiates and LiCl antagonizes noradrenergic responses. These results provide electrophysiological evidence for reciprocal adaptive changes in NE sensitivity, supporting results of biochemical studies.

Lithium transport across red cell membrane: a cell membrane abnormality in manic-depressive illness

In the families of manic-depressive patients, relatives with a history of affective disorders had a significantly higher ratio of mean red cell lithium to plasma lithium in vitro than relatives with no such history. A genetically controlled abnormality in lithium-sodium transport, the mechanism that determines the lithium ratio, may play a role in the etiology of some forms of affective disorders.

Effects of bicarbonate on lithium transport in human red cells

Lithium influx into human erythrocytes increased 12-fold, when chloride was replaced with bicarbonate in a 150 mM lithium medium (38 degrees C. pH 7.4). The increase was linearly related to both lithium- and bicarbonate concentration, and was completely eliminated by the amino reagent 4, 4'- diisothiocyanostilbene-2,2'-disulfonic acid (DIDS). DIDS binds to an integral membrane protein (mol wt approximately 10(5) dalton) involved in anion exchange. Inhibition of both anion exchange and of bicarbonate-stimulated lithium influx was linearly related to DIDS binding. 1.1 X 10(6) DIDS molecules per cell caused complete inhibition of both processes. Both Cl- and Li+ can apparently be transported by the anion transport mechanism. The results support our previous proposal that bicarbonate-induced lithium permeability is due to transport of lithium-carbonate ion pairs (LiCO-3). DIDS-sensitive lithium influx had a high activation energy (24 kcal/mol), compatible with transport by the anion exchange mechanism. We have examined how variations of passive lithium permeability, induced by bicarbonate, affect the sodium-driven lithium counter-transport in human erythrocytes. The ability of the counter-transport system to establish a lithium gradient across the membrane decrease linearly with bicarbonate concentration in the medium. The counter-transport system was unaffected by DIDS treatement. At a plasma bicarbonate concentration of 24 mM, two-thirds of the lithium influx is mediated by the bicarbonate-stimulated pathway, and the fraction will increase significantly in metabolic alkalosis.