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PubMed1991

NMR relaxation characteristics of rubidium-87 in perfused rat salivary glands.

Rubidium is a good substitute for potassium in many biological systems, and it has been suggested that rubidium-87 nuclear magnetic resonance (87Rb-NMR) spectroscopy could be used to measure K+ fluxes across membranes in intact tissues. To evaluate this possibility, isolated rat mandibular salivary glands were perfused with solutions containing Rb+ in place of K+. The 87Rb signals arising from the intra- and extracellular compartments were first separated by spectral subtraction and then subjected to line-shape analysis. The narrow extracellular signal was a single Lorentzian (line-width 156 Hz), whereas the broader intracellular signal consisted of two Lorentzian components (ca. 530 and 3080 Hz). Double-quantum filtering of the 87Rb signal from the glands revealed two components of transverse relaxation in antiphase (rate constants 1.8 and 13.3 ms-1), showing the probable involvement of quadrupolar interactions in the relaxation of intracellular Rb+. We conclude, therefore, that both line-shape analysis and double-quantum filtering could provide a basis for the measurement of unidirectional K+ fluxes in intact tissues.

Animals↗

PubMed2000

Measurement of rubidium and xenon absolute polarization at high temperatures as a means of improved production of hyperpolarized (129)Xe.

We report on a rubidium-xenon (Rb-Xe) polarization unit for the continuous production of large quantities of hyperpolarized (129)Xe. The unit includes two diagnostic systems which enable the absolute measurement of both the (85)Rb and (129)Xe polarization in situ and at high temperatures. The Rb diagnostic system allows the measurement of one- or two-dimensional images of the absolute Rb polarization and thus enables the experimental study of light penetration into the optical pumping cell. The equilibrium Xe polarization measured in the optical pumping cell and in the freezing unit is typically approximately 20%, under optimal flowing conditions, and this is much lower than the volume-averaged rubidium polarization.

Isotope Labeling↗

PubMed1983

Time-dependent excretion of lithium, sodium, potassium, rubidium, magnesium and strontium in the urine of a multiple sclerosis patient.

Field desorption mass spectrometry and stable isotope dilution have been used for direct trace analysis of metals in urine. Samples were collected over 24 h at 2 h intervals from a hospitalized multiple sclerosis patient. Quantitative determinations of Li+, Rb+, Mg2+ and Sr2+ from individual samples have been made and correlated with the amounts of urine excreted as well as with the time of day. The concentrations of Na+ and K+ were determined by flame photometry. The quantities of metals excreted in urine during the course of 24 h were 0.0129 mg for lithium, 4700 mg for sodium, 2100 mg for potassium, 1.4 mg for rubidium, 78.8 mg for magnesium and 0.2356 mg for strontium. The maximal absolute quantities excreted of all metals determined correspond with the largest volume of urine. The highest amounts of potassium, rubidium and strontium were found in urine during the daytime (8.00-20.00), whilst magnesium was excreted increasingly during the night hours (20.00-8.00). The excretion of lithium and sodium is fairly even over the entire 24 h period. It is noteworthy that similarities in the excretion profile and the concentration course are observed between Li+ and Na+ on one hand and between K+ and Rb+ on the other. Moreover, the lower concentration of Rb+ ions in urine of multiple sclerosis patients, in comparison to healthy individuals and clinical controls as reported previously, was confirmed.

Adult↗

PubMed2002

Simultaneous determination of potassium and rubidium content in yeast.

Rubidium is widely used as a potassium analogue in transport studies in yeast and other organisms. As rubidium (potassium) uptake is modulated by the internal potassium concentration, it is often necessary to determine both Rb(+) and K(+) concentrations in the same cell extract. Current methods based on atomic absorption/emission spectroscopy require separate analysis for each cation. Alternatively, unsafe radioactive isotopes can be used. Here we report a convenient, non-radioactive, HPLC/conductivity-based method that allows a complete analysis of both cations with a single injection from a cell extract. The increase in Rb(+) uptake during K(+) starvation in yeast is easily demonstrated with this method.

Biological Transport, Active↗

PubMed1977

The measurement of spleen perfusion in man: a non-invasive method using the ratio between Rubidium-81 and its decay product Krypton-81m.

A non-invasive method has been developed for measuring spleen perfusion in man. This involves recording the gamma-ray energy spectra over the spleen following the localisation of Rubidium-81 within the organ by injecting intravenously labelled heat denatured red cells. The spectra are analysed to provide the ratio of Rubidium-81 to its radioactive decay product Krypton-81 m. This ratio is dependent on the rate of perfusion through the organ. The difficulties encountered in applying this steady state method for monitoring tissue perfusion are illustrated and practical means for their solution presented. The results of applying this method to patients with various splenic disorders are presented and compared with those obtained by other workers using different monitoring techniques.

Humans↗

PubMed1983

Electrolyte metabolism in patients with periodic affective disorders during treatment with rubidium.

Five patients suffering from periodic affective disorders with short mood-cycles were treated with rubidium chloride, producing peak erythrocyte concentrations between 9 and 13 mmol/l. Loading with rubidium was associated with decreased total body potassium, but red-cell potassium was unchanged. Regular mood-cycling was disturbed, together with the associated body-weight changes. There was a slight extracellular "metabolic" acidosis. Electrolyte concentrations fluctuate abnormally in these patients, and two muscle biopsy specimens had very low potassium contents.

Affective Disorders, Psychotic↗

PubMed1975

Effects of diazepam on photosynthesis, respiration, rubidium uptake, and finestructure of Scenedesmus obliquus in synchronous cultures.

Effects of diazepam (Valium) on photosynthesis, chlorophyll/photosynthesis ratios, respiration, uptake of rubidium ions, and ultrastructure of Scenedesmus obliquus synchronized by a light-dark regimen of 14:10 hrs were determined. 80 and 160 muM diazepam, added to the nutrient medium at the start of the light-dark change (i.e., start of the cell cycle) gradually reduced rates of photosynthesis, below the initial rates from the beginning of the experiment. Contents of chlorophyll, however, remained nearly unaffected. Consequently, the diazepam-treated cells had a higher chlorophyll/photosynthesis ratio--also with regard to respiration in order to calculate the gross photosynthesis. The occurrence of photorespiration cannot be assumed. The net influx of rubidium was slightly reduced by 100 muM diazepam 0.5 and 2.0 hrs after the start of the cell cycle and was strongly inhibited after 5 to 14 hrs. 80 and 160 muM diazepam caused separation of thylakoids, formation of giant mitochondria and enlargement of vacuoles.

Adenosine Triphosphate↗

PubMed1986

Effects of isoproterenol on rubidium transport in slow- and fast-twitch muscles from euthyroid and hyperthyroid rats.

The influence of experimental hyperthyroidism on the catecholamine induced stimulation of rubidium ion transport in the soleus (SOL), a slow-twitch muscle and the extensor digitorum longus (EDL), a fast-twitch skeletal muscle of rats was studied. Thyroxine administration (800 micrograms/kg/day), for ten days induced a rise of ouabain-sensitive 86Rb uptake in SOL muscle, without affecting the ouabain-insensitive uptake, whereas both fractions of 86Rb uptake were increased in EDL muscle from hyperthyroid rats. Isoproterenol (5 mumol/l) caused a two-fold rise in ouabain-sensitive Rb uptake of euthyroid SOL muscle, while in hyperthyroid SOL it could stimulate only the ouabain-insensitive fraction of 86Rb influx. On the other hand, the stimulating action of isoproterenol on euthyroid EDL muscle was due to an enhancement of ouabain-insensitive Rb uptake, but in hyperthyroid EDL it failed to stimulate the ouabain-insensitive transport and caused a marked rise in ouabain-sensitive Rb uptake. The changes in catecholamine mediated transport properties in SOL muscle may be related to fibre type transformation induced by thyroid hormone, although in EDL the changes of catecholamine stimulation are unlikely due to fibre type conversion. Basal and isoproterenol stimulated cAMP levels were significantly reduced in both EDL and SOL muscles from hyperthyroid rats, in contrast with an insignificant decrease in net rubidium uptake caused by isoproterenol at the same concentration.

Animals↗

PubMed1979

Possible mechanism of rubidium-induced hyperactivity in the rat.

This study suggests that replacement of intracellular potassium by rubidium ions might lower the resting membrane potential. Thus rubidium-treated rats were more responsive to depolarizing influences and generated more cyclic AMP in the brainstem and consequently the behavioral changes.

Animals↗

PubMed1977

Investigations on trace elements in normal and senile cataractous lenses. Activation analysis of copper, zinc, manganese, cobalt, rubidium, scandium, and nickel.

A total of 125 human lenses (97 senile cataractous and 28 clear) were analyzed by means of neutron activation analysis for trace element concentrations of copper, zinc, manganese, cobalt, rubidium, scandium, and nickel. Tt was found that the rubidium concentration remarkably decreased and the copper concentration moderately increased with the progression of cataract. The concentrations of manganese, zinc, and cobalt showed some fluctuations without a definite increase or decrease, and the scandium and nickel content was found to be very low.

Age Factors↗

PubMed1985

Lack of effect of synthetic atrial natriuretic factor on rubidium uptake by human erythrocytes.

The effect of synthetic atrial natriuretic factor on the ouabain-sensitive and the furosemide-sensitive rubidium uptake by human erythrocytes has been studied. This peptide with potent diuretic and natriuretic effects did not affect any rubidium uptake system at concentrations of 10(-7) and 10(-9) M. These results do not support that the natriuretic effect is based on the inhibition of active transport systems in the renal tubules.

Atrial Natriuretic Factor↗

PubMed1976

Effect of rubidium on responses of rabbit vas deferens to transmural stimulation and to noradrenaline.

The effects of 2 mM RbCl on adrenergic transmission in rabbit vas deferens were investigated. Rubidium, but not potassium, markedly potentiated the sustained, secondary contractile response to transmural stimulation at 2--16 Hz. This effect was not abolished by indomethacin. Significant spontaneous desensitization to (--)-noradrenaline occurred, but this was prevented by the addition of 2 mM RbCl or KCl. Addition of 2 mM RbCl, but not of 2 mM KCl, significantly increased the amount of [3H] (+/-)-metaraminol released on transmural stimulation at 5 Hz, without affecting the uptake of [3H] (+/-)-metaraminol over a 30 min period. It is suggested that rubidium mainly potentiated responses of rabbit vas deferens to transmural stimulation by increasing transmitter release, possibly as a result of prolongation of the action potential.

Animals↗

PubMed1982

Trace element concentration in the human pineal body. Activation analysis of cobalt, iron, rubidium, selenium, zinc, antimony and cesium.

100 human pineal bodies (56 male and 44 females) were analyzed by means of instrumental neutron activation analysis for trace concentrations of cobalt, iron, rubidium, selenium, zinc, antimony and cesium. The results indicated that the measured element concentrations are not related to body-surface, age and fresh weight. Moreover, the mean absolute cobalt value from 97 pineal bodies is increased by a factor of 1.43 over the mean absolute concentration value of 257 other areas of the brain. The mean zinc content is found to be 3.7 fold higher than the mean zinc value from 269 other samples of brain. The iron values from various brain areas do not differ from those of the pineal body. Compared to other brain regions pineal selenium is increased and rubidium is decreased. Correlating the different element concentrations to each other, a positive correlation is found for selenium and ribidium, a negative correlation for cobalt and zinc. The present data suggest that the measured trace elements are somehow related to specific roles in the physiology and biochemistry of the pineal body. This is supported by the constancy of element concentration over a wide range of increasing fresh weights of the organ. It is considered that zinc, cobalt and iron are involved as constituents of enzymes in the metabolism of amino acids, peptides and proteins of the pineal body. Moreover the conspicuous high zinc content of this organ may be related to a so far undetected neurotransmitter.

Adolescent↗

PubMed1978

Alcohol consumption in rats treated with lithium carbonate or rubidium chloride.

Wistar-NTRU rats, offered a free choice between tap water and a 10% ethanol solution (v/v) in the absence of reinforcement, were injected for five days with Li2 CO3, RbCl or placebo. Lithium-treated group consumed 25% more liquid per day but chose to take 14.5% less alcohol than controls (p less than 0.05). By contrast, rubidium-treated animals consumed 15% less liquid but 70% more alcohol than control animals (p less than 0.005). Rubidium-treated rats were strikingly more active than the other two groups: their motility index was 60.0 as compared to 33.6 for lithium-treated and 29.4 for control rats. Serum glucose and urea nitrogen concentration were not significantly affected by the treatment but serum alcohol content was low in lithium-treated and high in rubidum-treated animals.

Alcohol Drinking↗

PubMed1994

Potassium, rubidium, and 4-aminopyridine effects on the circadian running rhythm in the hamster.

The period of the circadian rhythm of wheel-running was shortened when golden hamsters were given supplemental dietary potassium or rubidium for two weeks. Treatment with 4-aminopyridine, a potassium channel blocker, significantly increased circadian period. These period changes (0.17 h for potassium treatment, 0.14 h for rubidium, and 0.07 h for 4-aminopyridine) support previous data indicating that potassium is a component of the mammalian biological clock mechanism.

4-Aminopyridine↗

PubMed1996

Inhibition by lithium and rubidium of gentamicin-induced release of N-acetyl-beta-D-glucosaminidase from perfused rat kidney.

N-acetyl-beta-D-glucosaminidase (NAG) is one of the sensitive hydrolytic lysosomal enzymes which is released after renal tubular damages. We studied gentamicin-induced nephrotoxicity by determining the NAG release in perfused rat kidney. 100 micrograms/ml of gentamicin caused a time-dependent increase in enzymuria, peaking at 90 min. At this time the released NAG is about sixfold more than the control. The effect of concurrent perfusion with 100 micrograms/ml gentamicin and with 0.5 mmol/l lithium chloride or 0.5 mmol/l rubidium chloride in the perfusion fluid was also studied by measuring NAG activity in the perfusate. Both cations decrease the gentamicin-induced NAG release. However, the inhibitory effect of lithium chloride may be due to interference of this ion with the polyphosphoinositide cycle in renal tubular lysosomal membranes. There is no obvious evidence for an inhibitory effect of rubidium chloride.

Acetylglucosaminidase↗

PubMed1984

Lithium, sodium, potassium and rubidium cation concentrations during the development of certain organs of unborn rabbits.

The distribution of lithium, sodium, potassium and rubidium in rabbit fetuses was determined during the last two weeks of gestation. Samples of eye, brain, lung, heart, liver and kidney were investigated. Co-actions between the ion pairs Li+/Na+ and K+/Rb+ could be discerned. The essential properties of lithium and rubidium for the fetal development of rabbits were examined by investigating the supply of the fetal organs with these elements. Correlations between organ differentiation processes and metal concentrations were established and compared with the results obtained for the fetal development of other vertebrates.

Animals↗

PubMed1985

The mechanisms of action of noradrenaline on ouabain-sensitive rubidium uptake in guinea-pig myocardium.

The mechanism by which noradrenaline stimulates ouabain-sensitive rubidium uptake in guinea-pig myocardial tissue has been studied. The stimulatory action of low concentrations of noradrenaline was reversed by high doses of propranolol (10(-5) mol/l) in atrial tissue, but was not reversed by alpha- or beta-, or combined alpha- and beta- adrenoceptor antagonists in ventricular tissue. Rubidium uptake was also found to increase with increasing extracellular potassium concentration [( K]o). The percentage values of stimulation by noradrenaline decreased with increasing [K]o. Noradrenaline had no effect on the rate of ATP splitting by an isolated membrane preparation of Na,K-ATPase. It is proposed that noradrenaline stimulates active cation transport by either (a) an effect secondary to increased passive efflux of K ions, or (b) an action at a novel adrenergic receptor, distinct from the ATPase enzyme itself.

Animals↗