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At least 415 records · Page 23Linked to original sources
PubMed1995

Effects of clenbuterol and salbutamol on tissue rubidium uptake in vivo.

In anesthetized rats, injection of the beta 2-adrenoceptor (beta 2-AR) agonist clenbuterol (0.45 mumol/kg) caused a marked stimulation of 86RbCl (Rb) uptake by skeletal muscle, but had no effect on other tissues; soleus muscle showed the largest (144% increase) response. Injection of another beta 2-AR agonist (salbutamol 0.45 mumol/kg) had no effect on Rb uptake by any tissue except soleus muscle (83%). Both agonists increased body (colonic) temperature to the same extent. A 3-day treatment with salbutamol as a dietary admixture had no effect on body weight, muscle mass, or tissue Rb uptake, whereas the same treatment using clenbuterol produced significant increases in body weight and muscle mass and significant decreases in Rb uptake in three of the four muscle groups studied; Rb uptake in soleus was not affected. In another experiment, the short-term effect of clenbuterol injection on muscle Rb uptake was found to be resistant to a high dose (20 mg/kg) of the selective beta 2-AR antagonist ICI 118551. It was concluded that the selective effects of short-term administration of clenbuterol on muscle Rb uptake, coupled with its effects over 3 days on Rb uptake and muscle hypertrophy, implicate beta-AR modulation of cation transport (possibly via Na,K-adenosine triphosphatase [ATPase] activity) in the anabolic effects of clenbuterol on muscle protein deposition. Since the stimulation of Rb uptake by clenbuterol was resistant to high doses of a selective beta 2-AR antagonist and since salbutamol had little or no effect on muscle hypertrophy or Rb uptake, it is suggested that clenbuterol may exert its effects via an atypical beta-AR.

Adipose Tissue, Brown↗
PubMed1978

Cesium and rubidium salts: effects on voluntary intake of ethanol by the rat.

The effects of RbCl and CsCl on voluntary intake of ethanol solution by rats preferring ethanol solution 5% (w/w) over water as the drinking fluid was studied as a function of the dose given and the vehicle injected. Administration of RbCl or CsCl, 0.5 mEq/kg/day or 1.5 mEq/kg/day for three consecutive days, did not alter amounts of ethanol consumed. Repeated administration of RbCl or CsCl, 3.0 mEq/kg/day for three days, produced some moderate reduction in ethanol consumption. Simultaneous injection of RbCl (1.5 mEq/kg) and CsCl (1.5 mEq/kg) resulted in greater and profound lasting decrease in ethanol drinking. The later treatment did not alter specific activities of rat liver alcohol- and aldehyde dehydrogenase from saline treated controls. In general, dissolving the chloride salt of the alkali metals in saline resulted in greater effects on ethanol drinking than that determined after identical dose injected with water as the vehicle. The possible mechanism(s) underlying the effects of alkali metal salts used are suggested.

Alcohol Drinking↗
PubMed1984

Lithium, rubidium and cesium: cerebral pharmacokinetics and alcohol interactions.

The distribution of exogenously administered Li+, Rb+ and Cs+ in distinct mouse brain regions was studied as a function of time subsequent termination of a short-term daily treatment with these alkali metal salts. The resulting distribution profiles were compared with that obtained from the corresponding endogenous alkali metals. Endogenous Rb+ and Cs+ were readily measurable in all 6 brain regions studied compared to traces of measurable Li+. The Rb+ concentration was greater than that of Cs+. Short-term treatment with equal doses of the alkali metals studied showed greater brain accumulation of Rb+ and Cs+ than Li+ with a prolonged brain regions preference for Cs+ storages as a function of time. Duration of ethanol-mediated narcosis was reduced from saline controls by pretreatment with RbCl or CsCl as contrasted with prolongation by LiCl. The narcotic dosage of ethanol used reduced endogeneous Li+ and increased Cs+ levels in the cerebellum. This massive ethanol dosage exerted little effect on the distribution of exogenously administered Cs+ with exception of the striatum which continued to show a high content of Cs+. This may have contributed to partial antagonism of ethanol-depressant action and to restoring of motor function, i.e., rapid regaining of righting reflex. The results showed that Cs+ possessed longer biological life time in the brain than Rb+ or Li+ which may be of therapeutic value, i.e., in the use of Cs salts in treatment of brain tumors and in conjunction with psychoactive agents provided the respective chemotherapeutic and antidepressant properties of CsCl have been established.

Animals↗
PubMedDate not supplied

Extraction of radioactive rubidium and D-glucose from the artificially perfused intervillous space of the human placenta.

Extraction (Et) of 86Rb and [14C]D-glucose from the artificially perfused intervillous space of the human placenta was measured using [3H]L-glucose as a reference tracer. E. of 86Rb increased slowly from initial values near zero to a late maximum, which indicates that Et was greatly influenced by heterogeneity of indicator transit times through the intervillous space. The ascending part of the plot of -1n(I-Et) against time (t) of 86Rb was approximately linear. In each experiment the time corresponding to zero extraction was estimated by linear extrapolation of the plot. The mean of the times obtained in the individual experiments corresponded to the most frequent transit time of the indicators through the system outside the placenta. These observations suggest that 86Rb is taken up by the trophoblast from the entire space perfused. Under such conditions the rate of the trophoblast uptake can be estimated from the slope of the above plot. Unlike that of 86Rb, Et of [14C]D-glucose increased rapidly to a relatively steady level. This time course of Et may result from combined effects of transit time heterogeneity and rapid back-flux of the tracer.

Biological Transport, Active↗
PubMed1991

Screening for potassium channel modulators by a high through-put 86-rubidium efflux assay in a 96-well microtiter plate.

A rapid and sensitive 86Rb efflux assay to detect chemical compounds capable of modulating the ATP-dependent potassium (KATP) channel is described. This assay, which is performed in a 96-well microtiter plate, utilizes a substrate adherent cell line as the target, requires a small amount of 86Rb as the tracer, and is a suitable system for performing the biochemical and pharmacological characterization of the KATP-channel and its activators. Because this assay is amenable to automation, it presents a useful means for high-volume screening of chemical compounds on a routine basis.

Adenosine Triphosphate↗
PubMed1991

The effects of lithium, rubidium, cesium and magnesium ions on the close packing of persistence-length DNA fragments.

By application of scaled particle theory to persistence-length DNA fragments in sedimentation-equilibrium at speeds high enough to maintain close packing, the range of interhelical electrostatic repulsion was evaluated with LiCl, RbCl, CsCl, and MgCl2 as supporting electrolytes. Analysis of the data in terms of the Zimm cluster function confirmed that the net interaction between helices is purely repulsive in all cases. At constant ionic strength the electrostatic radius of the rod-like DNA decreases as the counterion changes from Li+ to Rb+ to Cs+. In contrast to univalent counterions, electrostatic radius increases with Mg2+ concentration, except at very low (mM) MgCl2 concentrations. All solutions undergo a reversible transition to a turbid, optically anisotropic phase at a slightly salt-dependent, critical DNA concentration, as observed previously for NaDNA.

Animals↗
PubMed1988

High perilymphatic potassium and rubidium levels modulate the sensory resting discharge in the isolated frog labyrinth.

The effects of high perilymphatic K+ and Rb+ concentrations (20 mM) on the posterior canal resting discharge have been examined in the isolated frog labyrinth. Both K+ and Rb+ produced an increase in spike frequency which is sustained by a parallel increase in the excitatory postsynaptic potential (EPSP) emission rate. High K+ and Rb+ levels reduce the size of the afferent spike, broaden its time course but do not induce repetitive activity at the axon level. The K+ and Rb+ facilitation proved to be inversely related to the fibre's initial resting activity. The facilitation produced by increased K+ was usually larger than that in Rb+ solution. High sensitive and low sensitive units with similar low resting discharge were detected in relation to their response either to K+ or Rb+. The effects of both ions can be explained on the basis of their interactions with the presynaptic hair cell currents.

Action Potentials↗