Determination of adenine, adenosine and related nucleotides at the low picomole level by reversed-phase high-performance liquid chromatography with fluorescence detection

Analysis of submicromolar concentrations of adenosine in plasma using reversed phase high-performance liquid chromatography

A method is described for the determination of adenosine in small samples of plasma (< 1 ml) using reversed-phase high-performance liquid chromatography (HPLC) in either a simple isocratic or a gradient elution system which gives a clear separation of adenosine from other plasma constituents. Acetone is used to deproteinize plasma and chloroform to remove unwanted lipid soluble material prior to HPLC. 6-Methyladenosine is used as an internal standard for making corrections for changes in concentration during sample processing. Adenosine in plasma could be reliably detected at concentrations lower than its minimum effector concentration as a vasodilator (4 x 10(-8) Mol l(-1) using the isocratic system and 1.9 x 10(-8) Mol l(-1) with gradient elution). The recoveries of adenosine added to blood at concentrations ranging from 2 x 10(-8) Mol l(-1) to 1.4 x 10(-6) Mol l(-1) were from 101.4 +/- 16.9% (n = 4) to 100.0 +/- 3.6% (n = 5). The present method provides a simple, sensitive and selective assay for submicromolar concentrations of adenosine in plasma with good recovery.

Simultaneous determination of six adenyl purines in human plasma by high-performance liquid chromatography with fluorescence derivatization

A sensitive method was developed for the simultaneous determination of six adenyl purines in human plasma by high-performance liquid chromatography. The adenyl purines (adenine, adenosine, AMP, ADP, ATP and cyclic AMP) were derivatized using 2-chloroacetaldehyde for fluorescence detection, and the reaction and separation conditions were reinvestigated to improve sensitivity for small volume sample analysis. Each derivatized purine was separated on a Capcell Pack SG120A column with mobile phase consisting of 0.05 M citric acid-0.1 M dipotassium hydrogen phosphate (pH 4.0)-methanol (97+3). The detection limits were 100-1000 fmol/ml by fluorescence detection, some 500 times better than previous reports. The proposed method was applied to determine adenyl purines in human plasma. The purine levels were as follows: ATP (9.2-22.2 pmol/ml), ADP (5.5-22.2 pmol/ml), AMP (0.8-3.2 pmol/ml). Other purines, adenine, adenosine, cAMP were lower than 0.1 pmol/ml.

Determination of ATP and its metabolites released from rat caudal artery by isocratic ion-pair reversed-phase high-performance liquid chromatography

A sensitive and selective assay method for adenine compounds (purines) using high-performance liquid chromatography with fluorescent detection was developed. The 1,N6-ethenoderivatives of adenine, adenosine, AMP, ADP, and ATP formed by reaction with chloroacetaldehyde at 80 degreesC were separated by ion-pair reversed-phase chromatography within 15 min under isocratic conditions. alpha,beta-Methylene adenosine 5'-diphosphate could be used as an internal standard for the determination of purines. The calibration graphs constructed with peak area ratios against amounts were linear between 0.1 and 10.0 pmol of each purine. The repeatability and intermediate precision were less than 6% (RSD, n = 5) and 8% (RSD, n = 3), respectively, at 0.5 pmol of each purine. A method for calculation of each purine amount which considers hydrolysis by derivatization is described. The optimized method was applied to determine the purines released from the rat caudal artery stimulated by noradrenaline.

Determination of guanine and its nucleosides and nucleotides in human erythrocytes by high-performance liquid chromatography with postcolumn fluorescence derivatization using phenylglyoxal reagent

A high-performance liquid chromatographic method with on-line postcolumn fluorescence derivatization is described for the simple and sensitive determination of guanine and its nucleosides and nucleotides in human erythrocytes. After deproteinization of the biospecimen, guanine and its nucleosides and nucleotides were separated on a reversed-phase column (TSKgel ODS-120T) by gradient elution with methanol in the aqueous mobile phase consisting of tetra-n-propylammonium phosphate (pH 6.0) and phosphate buffer (pH 6.0). The compounds were then automatically converted into fluorescent derivatives by reaction with phenylglyoxal. This derivatization was selective for guanine-containing compounds. The present method permitted the reliable quantification of GDP and GTP in human erythrocytes. The detection limits (at a signal-to-noise ratio of 3) for guanine and its nucleosides and nucleotides were 3.2-10.0 pmol in a 20-microliters injection volume. The concentrations of GDP and GTP in human erythrocytes were 17.2 +/- 6.2 and 40.2 +/- 5.8 nmol/ml, respectively.

High-performance liquid chromatography of the adenosine A1 agonist N6-cyclopentyladenosine and the A1 antagonist 8-cyclopentyltheophylline and its application in a pharmacokinetic study in rats

This report describes a rapid and sensitive analysis for the simultaneous detection of the adenosine A1 receptor ligands N6-cyclopentyladenosine (CPA) and 8-cyclopentyltheophylline (CPT) in rat blood. The method involved alkaline extraction of the compounds and internal standard N6-cyclohexyladenosine (CHA) with ethyl acetate, followed by isocratic reversed-phase high-performance liquid chromatography on a 3-microns MicroSphere C18 column with UV detection at 269 nm. The mobile phase consisted of a mixture of 10 mM acetate buffer (pH 4.0)-methanol-acetonitrile (56:40:4, v/v/v) with a flow-rate of 0.50 ml/min. The total run time was ca. 19 min. For CPA and CPT extraction yields were greater than 77 and 66% in the concentration range of 0.010-0.75 microgram/ml and 0.025-15 micrograms/ml, respectively, with intra- and inter-assay variations less than 9%. In 100 microliter blood samples the corresponding limits of detection were 3.3 and 6.2 ng/ml (signal-to-noise ratio = 3). CPA was found to be degraded in rat blood in vitro with a half-life of 24 min at 37 degrees C. The utility of the analytical method was established by analyzing blood samples from rats which had received an intravenous administration of 200 micrograms/kg CPA or 12 mg/kg CPT. Due to its rapidity and sensitivity this method is concluded to be particularly useful in pharmacokinetic studies with CPA and CPT.

Determination of 9-[(2-phosphonylmethoxy)ethyl]adenine in rat urine by high-performance liquid chromatography with fluorescence detection

A high-performance liquid chromatographic (HPLC) method for the determination of 9-[(2-phosphonylmethoxy)ethyl]adenine (PMEA) in urine is described. The procedure includes treatment of the urine sample with chloroacetaldehyde to form the fluorescent 1,N6-ethenoadenosine derivative, which was analyzed by reversed-phase HPLC with fluorometric detection. Validation of the method showed good sensitivity, precision and reproducibility. The method is useful for the study of urinary excretion of PMEA in the rat.

High-performance liquid chromatographic analysis of ascorbate-2-phosphate, adenine and hypoxanthine in stored human blood

A high-performance liquid chromatographic procedure was developed to assay for adenine, hypoxanthine, and ascorbate-2-phosphate in both red blood cells and plasma. The samples were diluted and filtered through Centriflo filter cones to remove most of the blood proteins before injection onto the column. The application of the technique to an experimental blood preservation study is illustrated.

Analyses of adenosine and adenine nucleotides in biological materials by fluorescence reaction-high-performance liquid chromatography

A previous method of determination of adenine compounds by high-performance liquid chromatography, using bromoacetaldehyde as a fluorescent reagent and a column of Hitachi gel No. 3012-N, was improved and extended to biological materials, especially to measure enzyme activities. A column packed with finer beads, Hitachi gel No. 3013-N, was found to be better than that of No. 3012-N, judging from the analysis time and resolution. ADP, from the hydrolysis of ATP by Na, K-ATPase, was determined quantitatively, and the enzyme activity was inhibited with ouabain. cAMP obtained from ATP by reaction with adenylate cyclase was also determined in the presence of various concentrations of L-epinephrine or sodium fluoride. The ATP levels in human blood were determined, and the cellular levels of ATP and ADP in neuroblastoma N1E 115 were examined as a function of cell growth.

Evidence for negative control of growth by adenosine in the mammalian embryo: induction of Hmx/+ mutant limb outgrowth by adenosine deaminase

We investigated the growth-regulatory actions of adenosine and adenosine deaminase (ADA) during embryonic limb development in the mouse. Polydactylous outgrowth, an expression of the Hemimelia-extra toe (Hmx/+) mutant phenotype, was experimentally regulated in hindlimb buds explanted into a serum-free in vitro system at stage 18 of gestation. Its expression was promoted by exposure to 0.1 or 0.2 IU/ml exogenous ADA and suppressed by co-exposure to 10 nM (-)-N6-(R-phenylisopropyl)-adenosine (N6-PIA). Evidence that N6-PIA acted as a high-affinity agonist against the external adenosine receptor was provided by experiments in which 100 microM caffeine, a known antagonist, competitively blocked its effect. The endogenous adenosine content was analyzed by reversed-phase high-performance liquid chromatography with fluorometric detection following its conversion to the 1,N6-ethenoadenosine derivative. At stage 18, the adenosine levels were 0.5 pmol/micrograms DNA in whole embryos and 0.08 pmol/micrograms DNA in hindlimb buds. At the same stage, partially purified extracts of the embryonal plasma enriched fraction contained high levels of ADA activity (0.04-0.06 IU/embryo, or 0.7-1.0 IU/mg protein). In contrast, blood cells contained 0.0001 IU/embryo (or 0.01 IU/mg protein). This enzyme occurred as a single kinetic form with a molecular weight of 45000-47000 daltons and an apparent Km of 36-38 microM. Its presence in the embryonal plasma argues against an endocrine mechanism of adenosine secretion in favor of autocrine (self-regulatory) or paracrine (proximate-regulatory) mechanisms. Taken together, our results suggest that the in vitro outgrowth of the prospective polydactylous region is induced upon escape from the local growth-inhibitory influence of extracellular adenosine.(ABSTRACT TRUNCATED AT 250 WORDS)

Measurement by fluorescence of interstitial adenosine levels in normoxic, hypoxic, and ischemic perfused rat hearts

An improved assay was used to investigate the effects of hypoxia or ischemia on interstitial fluid and coronary venous effluent levels of adenosine in isolated perfused nonworking rat hearts. The adenosine in 5- to 10-microliter samples of left ventricular epicardial surface transudates and coronary effluents was reacted with chloroacetaldehyde, and the fluorescent derivative (1,N6-ethenoadenosine) was quantitated using high pressure liquid chromatography and fluorescence detection. Hearts responding to hypoxia could be separated into two groups. In one group of hearts, the control (normoxic) transudate and effluent adenosine concentrations were 94 +/- 24 and 41 +/- 6 pmol/ml, respectively. These values increased by 118 and 96%, respectively, with 5 minutes of hypoxia (30% O2), and returned to control levels 5 minutes after resumption of normoxia. In a second group of hearts, the normoxic control levels of adenosine in the transudates (42 +/- 7 pmol/ml) and coronary effluents (62 +/- 17 pmol/ml) were increased with hypoxia by 174 and 1,178%, respectively. However, the transudate levels continued to rise for 5 minutes after resumption of normoxic perfusion while effluent levels fell. In another series of hearts, global ischemia for 30 seconds elicited an elevation of transudate adenosine levels by 362 to 641% above control (58 +/- 15 pmol/ml) as determined 30 seconds after resumption of perfusion flow.(ABSTRACT TRUNCATED AT 250 WORDS)

Determination of adenosine ribo- and deoxyribonucleotides as their 1-N6-etheno derivatives by reversed-phase ion-pair high-performance liquid chromatography

The chromatographic resolution of fluorescent 1-N6-etheno derivatives of adenine and adenosine ribo- and deoxyribonucleotides on reversed-phase columns has been optimised by a systematic study of the effect of ion-pair concentration, pH, eluent molarity and methanol concentration. Using tetrabutylammonium hydrogen sulphate as the ion-pair separation of up to eight derivatives could be achieved in ca. 10 min. Conditions of derivatisation with chloroacetaldehyde have been investigated in order to reduce hydrolysis of the nucleotides.

Effects of synaptic activity on the metabolism and release of purines in the rat superior cervical ganglion

The release of radioactive metabolites from isolated rat superior cervical ganglia was measured under various conditions following preloading with 3H-adenosine. The 3H label was recovered primarily in the adenosine metabolites, ATP, ADP, AMP, IMP, and inosine, rather than in adenosine itself. Increased release was evoked by preganglionic stimulation or by exposure to a high-K+ medium, whereas in a low-Ca2+-high-Mg2+ medium, both spontaneous release and evoked release of most metabolites were inhibited. Exposure of the ganglion to an atmosphere of N2 also increased the release of most labeled metabolites, but this release was not substantially affected by a low-Ca2+ medium. The fluorescent derivatives of the endogenous adenine-containing compounds present in the ganglion were prepared from homogenates and separated by high-performance liquid chromatography (HPLC). By the end of the testing period (6 hr), levels of ATP in the isolated ganglia had dropped to 10-20% of the initial values, while levels of ADP, AMP, and adenosine increased. There was little difference in these values between nonstimulated ganglia and those exposed to N2 or to a high-K+ medium.

Uptake and metabolism of [3H]adenosine by Aplysia ganglia and by individual neurons

[3H]Adenosine was taken up and metabolized by isolated ganglia of the marine mollusc Aplysia californica. After 2 h, most of the radioactivity was recovered as metabolites, including ATP, ADP, and AMP, as well as the deaminated products, inosine, hypoxanthine, and uric acid. Little remained in the form of adenosine. These pathways were not uniformly distributed among various tissue elements. In most individual neurons, inosine and its breakdown products were the principal metabolites of [3H]adenosine, whereas ATP and other nucleotides predominated in the connective tissue sheath. Endogenous levels of ATP, ADP, AMP, and adenosine in ganglia, sheath, and individual neurons were also determined using a fluorimetric-HPLC assay. The concentrations of the nucleotides were quite uniform in sheath and among the individual neurons assayed (1-5 pmol/microgram of protein); however, concentrations of adenosine were considerably higher in neurons than in the sheath.

Sugar uptake into Allium cepa leaf tissue: an integrated approach

Allium cepa L. leaves were subjected to enzymatic (pectolyase) and mechanical manipulation in order to ascertain the contribution made by various leaf tissues to the total sugar uptake by the leaf. In order to develop an understanding of the basic anatomy and ultrastructure of the Allium leaf and assess the integrity of the tissue before and after enzymatic and mechanical manipulation, a light- and transmission-electron-microscopy study was performed. One outcome of this study was the discovery that the chloroplasts of the bundle-sheath cells contain starch. The function of these inclusions in relation to carbohydrate pools and translocation is discussed. Kinetic curves for sucrose and fructose uptake by leaf discs derived from control and modified leaves are presented. In addition, kinetic curves for the tissues removed by the enzymatic treatment (inner parenchyma, bundle sheath and some vascular parenchyma) and the vascular bundles were also obtained. All tissues exhibited the same linear plus saturable profile as the dicotyledon, Beta vulgaris, with the exception of fructose uptake into the inner parenchyma and bundle-sheath cells; in this case the response was linear. The effect of anoxia on uptake of exogenous sucrose was also investigated. Anaerobiosis inhibited both the linear and saturable component of sucrose influx. Adenine-nucleotide levels were obtained using high-performance liquid chromatography for control (air) and anoxia-treated (N2) leaf discs. A general loss of adenine nucleotides was observed. The results presented indicate that all tissues of the leaf retrieve exogenous sugar such that the kinetic curves derived from leaf discs cannot represent phloem loading, per se.

Sensitive fluorimetry of adenine-containing compounds with high-performance liquid chromatography

A definitive method to determine adenine compounds simultaneously was established by introducing a new fluorescent reagent into high-performance liquid chromatography. Bromoacetaldehyde was the best reagent among the haloacetaldehydes examined. A quantitative reaction was obtained even for unstable ADP and ATP. A high resolution of adenine nucleotides was obtained using a column of Hitachi gel No. 3012-N. The method was applied to the measurement of cyclic AMP in urine, and ADP and ATP in brain and blood. Further, the sensitivity of the method was increased by a new fluorescence spectrophotometer constructed for micro-HPLC. Femtomole amounts of the adenine nucleotides were clearly separated.