Separation of ribonucleotides, deoxynucleotides, cyclic nucleotides and deoxycyclic nucleotides by reversed-phase high-performance liquid chromatography

Determination of 2-chloro-2'-deoxyadenosine nucleotides in leukemic cells by ion-pair high-performance liquid chromatography

A specific isocratic ion-pair HPLC method for the quantitation of mono-, di- and triphosphates of 2-chloro-2'-deoxyadenosine (CdA) in leukemic cells from patients is described. The method is based on an extraction of nucleotides from cells with a solution of perchloric acid containing triethylammonium phosphate followed by an isocratic separation on an Ultrasphere ODS column (250 x 4.6 mm, 5 microns) with a mixture of 89% triethylammonium phosphate buffer (0.08 M, pH 6.1) and 11% methanol as the eluent. UV absorbance at 265 nm was used. The limit of detection was 65 nM. Standard curves for the CdA triphosphate (CdATP) were linear within the concentration range of 200 nM to 12 microM. The mean overall recovery of CdATP was 90% within a concentration range of standard curves. The within-day and day-to-day coefficients of variation at concentrations of 1.44 microM and 6.25 microM CdATP were < 10%. The applicability of the method was demonstrated by in vitro studies of the accumulation of CdA mono-, di- and triphosphates in CCRF-CEM cells and by determination of the cellular pharmacokinetics of CdA nucleotides in leukemic cells from a patient treated with CdA.

Comparative performance of ion exchange and ion-paired reversed phase high performance liquid chromatography for the determination of nucleotides in biological samples

We have compared anion exchange chromatography on APS-Hypersil (4.6 x 100 mm) eluted with a phosphate gradient with reversed phase chromatography on ODS-Hypersil (4.6 x 100 mm) in the presence of either tetrabutylammonium (TBA) or triethylammonium (TEA) ions with a methanol gradient. The systems have been compared both for ease of operation and for their resolving power with standard mixtures and acid extracts of both normal red cells (RBC) and ischaemic tissues. The two chromatographic modes exhibited similar separating efficiencies for standard mixtures of nucleotides but retention times were most stable using reversed phase liquid chromatography (RPLC) with TEA. Anion exchange columns slowly lost ion exchange capacity but selectivity was unchanged. RPLC in the presence of TBA gave reproducibile capacity factors only when operated isocratically due to irreversible changes to the silica surface. For RBCs the RPLC with TEA and anion exchange systems resolved 17 and 15 peaks, respectively, and for the ischaemic samples 22 and 14 peaks, respectively. However, nucleosides and bases were also resolved by the ODS column causing chromatographic crowding and uncertain peak identification.

The high performance liquid chromatography of enzyme systems relating to purine and pyrimidine metabolism: an overview

Purines and pyrimidines are now routinely separated by HPLC. By careful selection of chromatographic conditions which match the expected changes in hydrophobicity and/or ionic nature of the substrate and products most enzymes of the purine and pyrimidine salvage pathways can be routinely and accurately determined. Ion-paired reversed-phase systems are often the most advantageous. The relevance of such assays to biomedical analysis including their role in the diagnosis of inborn errors of metabolism is stressed.

Isocratic reversed-phase high-performance liquid chromatography of ribonucleotides, deoxynucleotides, cyclic nucleotides and deoxycyclic nucleotides

An isocratic reversed-phase high-performance liquid chromatographic system is described for the separation of a relatively large number (greater than 20) of ribonucleotides, deoxynucleotides, cyclic nucleotides and deoxycyclic nucleotides. A 25 cm x 5 mm ODS-Hypersil (5 microns particle size) column was used with methanol-triethylammonium phosphate buffer as eluent. The effects of methanol content, pH, and ionic strength of the buffer on retention and resolution of the nucleotides have been studied. The applicability of the system was demonstrated by the analysis of nucleotides in cells and tissue extracts.

An 'in situ' perfusion system suitable for investigating mammary-tissue metabolism in the lactating rat. Hormonal regulation of acetyl-CoA carboxylase

A technique is described for the non-recirculating perfusion of inguinal/abdominal mammary tissue in situ in anaesthetized lactating rats. Tissue viability was maintained, without resort to infusion of vasoactive chemicals which may also be effectors of cellular metabolism, for at least 90 min. Total tissue adenine nucleotides (per mg of DNA) were somewhat decreased in perfused relative to non-perfused mammary tissue. DNA content (per g wet wt. of tissue) was diminished after 90 min of perfusion to approx. 65% of its value in control tissue. Adenylate energy-charge ratios were lower in perfused tissue in the absence of hormones than in control tissue. They were increased to control values by the presence of either insulin or isoprenaline in the perfusate. No changes occurred in flow rate of the perfusate that might account for these increases. In mammary tissue perfused without addition of hormones, acetyl-CoA carboxylase activities were similar to those measured in control tissue samples, although activity-ratio measurements implied some increase in the phosphorylation of this enzyme. Insulin or isoprenaline increased the activity of acetyl-CoA carboxylase, especially when this was measured at low concentrations of citrate. Confirming conclusions from previous experiments with mammary acini and explant preparations, insulin activated acetyl-CoA carboxylase in mammary tissue, but inhibition of its activity was not mediated by cyclic AMP.