Lithium uptake at physiological ion concentrations in a human clonal neuroblastoma cell line

Lithium distribution in mania: single-dose pharmacokinetics and sympathoadrenal function

We examined lithium distribution after a single dose of 25 mEq in 14 drug-free manic patients. Lithium concentrations were measured in plasma, red blood cells, and urine. Maximum concentrations of lithium, times at which they were attained, and influx and efflux rate constants for extracellular fluid, red blood cell, and muscle-like compartments were estimated using a three-compartment pharmacokinetic model. Tissue lithium concentrations may continue to increase for hours after plasma lithium concentrations have peaked. Rate constants for absorption, excretion, and influx and efflux for the tissue compartments were similar to those previously reported for normal subjects. Rate constants for transport into and out of the tissue compartments correlated negatively with norepinephrine or epinephrine excretion and positively with the plasma/red cell Na+ gradient. Rate constants for efflux from red blood cell and muscle compartments correlated with measures of adrenocortical function and were higher in dexamethasone nonsuppressors than in suppressors. These data show that distribution of lithium may be related to sympathodrenal activity and Na+ distribution in manic patients.

Selective determination of lithium in biological fluids using flow injection analysis

The use of flow injection analysis to automated extraction methods for the determination of lithium ion utilizing crown ethers or cryptands is demonstrated. The ion-pair extraction of cryptand 211, lithium, and resazurin exhibits a linear range for lithium ion of 70 ppb to 2.1 ppm. This method could tolerate up to 1000 ppm sodium ion. The chromogenic crown ether, 1-(2-hydroxy-5-nitrobenzyl)-1-aza-4,7,10-trioxacyclododecane, exhibits a linear range for lithium ion of 0.3 to 2 ppm. A sodium ion concentration of 230 ppm can be tolerated. Both extraction systems were used in the automated determination of lithium in blood serum and urine. Both methods agreed well with the known and/or atomic absorption values.

Matrix modifiers in graphite furnace atomic absorption analysis of trace lithium in biological fluids

The use of KH2PO4/NH4NO3 as matrix modifier eliminates severe interference effects on the atomic absorption analysis of lithium in biological fluids. This enables determination of trace lithium in microliter size samples with absolute sensitivity (0.0044 absorbance) of 2 pg. There is no requirement for standard additions experiments to correct for interferences in specific matrices such as serum and saliva. The biological half-life of trace lithium was 16.9 +/- 2.8 h. Saliva lithium is a good estimate of serum level; the two are highly correlated (r = 0.97) and saliva level is about three times serum.

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.

Effects of lithium on electrical activity and potassium ion distribution in the vertebrate central nervous system

Three different regions of the vertebrate central nervous system maintained in vitro (frog spinal cord, guinea pig olfactory cortex and hippocampus) have been used to investigate how Li+ influences membrane potential, membrane resistance, action potentials, synaptic potentials and the transmembrane K+-distribution of neurons and glial cells. In view of the therapeutic action of Li+ in manic-depressive disease, a special effort was made to determine the threshold concentration for the actions of Li+ on the parameters described above. It was observed that Li+ induced a membrane depolarization of both neurons and glial cells, a decrease of action potential amplitudes, a facilitation of monosynaptic excitatory postsynaptic potentials and a depression of polysynaptic reflexes. The membrane resistance of neurons was not altered. Li+ also induced an elevation of the free extracellular potassium concentration and a decrease of the free intracellular potassium concentration. Furthermore, in the presence of Li+ a slowing of the recovery of the membrane potential of neurons and glial cells, and of the extracellular potassium concentration after repetitive synaptic stimulation was observed. The threshold concentrations for the effects of Li+ were below 5 mmol/l in the frog spinal cord and below 2 mmol/l in the guinea pig olfactory cortex and hippocampus. The basic mechanism underlying the action of Li+ may be an interaction with the transport-function of the Na+/K+ pump.

Lithium entry into neural cells via sodium channels: a morphometric approach

Rat cerebral cortical explants prepared from 18-day-old embryos were grown for 18 days in vitro. Cultures were exposed to Na+, Li+ and choline+ media, respectively, in the presence or absence of tetrodotoxin and/or veratridine, and processed for electron-microscopy. Veratridine (50 microM) induced an increase in summated and mean areas of neuronal profiles in Na+- and Li+-media but not in the choline+-medium: the summated perimeters did not change. The mean value of the neuronal form factor was significantly elevated following exposure to veratridine in a Na+- or Li+-dependent manner, indicating that the shape of the sectioned neuronal elements shifted towards an (ideal) circle. Qualitative assessment revealed an increased electron-lucency of the cytoplasm of neuronal profiles in Na+- and Li+-media containing veratridine. The veratridine-induced neuronal changes were inhibited by simultaneous addition of tetrodotoxin (1 microM) to the media. In the case of the glial cells, the values of the summated area and form factor did not change in the various experimental groups. The area of the extracellular space per unit area of sections significantly decreased in the Na+- and Li+-media following veratridine exposure; this did not occur in the choline+-medium. The results indicate a considerable swelling of the neuronal elements, reflecting cation, Cl- and water uptake following prolonged sodium channel activation in the presence of Na+ or Li+ ions. The quantitative ultrastructural data strongly suggests an entry of Li+ ions into cultured rat cerebral cells via sodium channels.

Indirect ultrastructural evidence for lithium uptake by cultured rat cerebral cells through the sodium channel

Cerebral cortices, prepared from 18-day-old rat embryos, were grown in explant cultures for 18 days. They were then incubated for 25 min in media of 3 types of cationic composition with and without tetrodotoxin and/or veratridine. Qualitative and quantitative ultrastructural observations revealed a considerable swelling of neuronal elements following veratridine exposure in both Na+ and Li+ media; this swelling was prevented by tetrodotoxin. By contrast, veratridine failed to induce swelling of neuronal profiles in a choline+ medium. The results indirectly indicate that Li+ ions enter cultured rat cerebral cells through the Na+ channels.