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PubMed1992

Implementation and evaluation of a two-compartment model for quantification of myocardial perfusion with rubidium-82 and positron emission tomography.

Positron emission tomography offers the ability to noninvasively assess regional myocardial perfusion in absolute terms (i.e., milliliters per gram per minute). Accurate estimates have been difficult to achieve with generator-produced 82Rb because of the complex behavior of this tracer in the myocardium. The aim of the present study was to determine whether regional myocardial blood flow could be assessed quantitatively with 82Rb and positron emission tomography by using a two-compartment kinetic model. Regional perfusion in milliliters per gram per minute was estimated from dynamic tomographic scans after intravenous administration of 82Rb in 18 studies in 13 intact dogs studied without intervention, after 2 and 24 hours of induced ischemia, during reperfusion after transient occlusion, or at rest and after pharmacological hyperemia after induced coronary artery stenosis. Regional flow was estimated along with the forward and backward rates of transport (k1 and k2 [minutes-1]) after the relative volume of distribution of the first compartment was fixed to 0.53 ml/ml and the tomographic parameters, the recovery and spillover fractions, were fixed to averaged values obtained in previous studies. In 36 comparisons, estimates of regional flow with 82Rb correlated well with flow measured with concomitantly administered radiolabeled microspheres (r = 0.91, p less than 0.05) over the flow range from 0.14 to 4.25 ml/g/min. A putative index of viability, k2, increased significantly in regions with severe ischemia. The results suggest that quantification of regional myocardial perfusion is possible in centers using 82Rb for estimates of myocardial perfusion when a physiologically appropriate, two-compartment model is used.

Animals↗
PubMed1983

Comparison of the effects of rubidium and potassium on renin secretion from rat kidney slices.

It has been shown previously that both low (less than 2 mM) and high (greater than 45 mM) concentrations of extracellular K inhibit the renin secretory rate of rat kidney slices, and that nonidentical Ca-dependent mechanisms appear to be involved. As Rb can substitute for K in many biological systems, the present experiments were designed to compare the effects of K and Rb on renin secretion of rat kidney slices. Adding either KCl or RbCl to a nominally K-free incubation medium stimulated renin secretory rate in concentration-dependent manners; secretory rate was half-maximally stimulated at approximately 1.5 mM and maximally stimulated at approximately 2-3 mM concentrations of either KCl or RbCl. Ouabain completely abolished the basal secretory rate, in either KCl- or RbCl-containing media. These results suggest that the effects of increasing KCl or RbCl in the range of 0.5-4 mM are attributable to stimulatory effects of Rb and K on Na-K-ATPase activity. Renin secretory rate was greatly inhibited by incubating kidney slices in media containing 60 mM concentrations of either KCl or RbCl. A concentration of methoxy-verapamil which completely blocked the inhibitory effects of 60 mM KCl or of 60 mM RbCl failed to antagonize the inhibitory effects of a nominally K-free medium or of media containing ouabain and either 4 mM KCl or 4 mM RbCl. Taken together with previous results, these observations suggest that Rb can substitute for K in the renin secretory process. Furthermore, they support the hypothesis that inhibitors of Na-K-ATPase, and depolarization inhibit renin secretion by Ca-dependent mechanisms which are not identical.

Animals↗
PubMed1984

Effects of 5-hydroxytryptamine on rubidium ion fluxes and insulin release in cultured pancreatic islets.

We have incubated pancreatic islets isolated from noninbred ob/ob mice and NMRI mice for 3 days with or without 5-hydroxytryptamine (5-HT) in the medium and tested the effect of such long term treatment on subsequent insulin release and 86Rb+ accumulation and efflux. Two tenths millimolars of 5-HT abolished insulin release in response to 20 mM glucose. Two tenths millimolars of 5-HT also diminished the ability of islets to accumulate 86Rb+ and the effect of 10 mM glucose on 86Rb+ efflux. One one-hundredth millimolars of 5-HT had no effect on insulin release or 86Rb+ fluxes. Clearly, islets subjected to 5-HT for 3 days at concentrations that do not elicit demonstrable effects in short term incubations show a reduced secretory response. However, the physiological role of the high affinity uptake system for 5-HT in islet cells [Michaelis-Menten constant (Km) = 1.6 microM] remains unknown.

Animals↗
PubMed2005

Electrospray ionization mass spectrometry of pyrimidine base-rubidium complexes.

Nucleobases and alkali metal cations, under electrospray ionisation conditions, tend to form the so-called magic number clusters (unusually stable clusters in comparison with the neighbouring ones). The effect of the ion source parameters, namely cone voltage and desolvation temperature and relative concentrations of thymine and RbCl on the [T5+Rb]+ ion abundance has been studied.

Hydrogen Bonding↗
PubMed2003

Trace analysis of rubidium hyperfine structure in a flame atomizer using sub-Doppler laser wave-mixing spectroscopy.

Nonlinear laser wave mixing is a versatile spectroscopic method for trace elemental analysis at high spectral resolution. Sub-Doppler spectral resolution allows isotope and hyperfine structure measurements of some of the elements even when using a room-pressure analytical flame (i.e., sub-Doppler but Lorentzian broadened spectra). A non-planar wave-mixing optical setup offers some advantages as compared to the conventional planar wave-mixing setup including better signal collection efficiency and easier optical alignment. Using our absorption-based wave mixing, a detection limit of 0.05 ng/mL (i.e., 50 parts-per-trillion) is reported for Rb in an air/acetylene flame, while still maintaining sub-Doppler spectral resolution for the infrared 780.0-nm Rb transition line.

Absorption↗
PubMed2004

Use of rubidium, manganese, and zinc as tracers to measure intestinal permeability by PIXE analysis: basal study in an experimental enteritis model.

Intestinal permeability has been suggested to be closely linked with the etiology or activity of Crohn's disease. However, current methods for measurement of intestinal permeability are too laborious for routine examination, as they require urine collection and/or use of radioisotopes. The present study was performed to develop a more convenient and safer method for assessing intestinal permeability using blood samples rather than urine. Rats with indomethacin-induced enteritis were orally administered Rb, Mn, and Zn as tracers. Intestinal permeability was determined by assaying the levels of Rb, Mn, and Zn in blood samples by particle-induced X-ray emission (PIXE). The distributions of Rb, Mn, and Zn in the small intestine after administration were analyzed by micro-PIXE. The conventional PIXE analysis showed that the levels of Rb and Zn in the blood in the enteritis group were correlated with the grade of enteritis. The micro-PIXE analysis showed that Rb, Mn, and Zn were translocated into the wall of the proximal small intestine 5 min after administration, and this effect was more conspicuous in the enteritis group than in controls. Analysis of blood or small intestine tissue samples using the PIXE allows determination of both intestinal permeability and the route of permeation.

Animals↗