Methodological aspects on the firefly luciferase assay of adenine nucleotides in whole blood and red blood cells

Human plasma ATP concentration

BACKGROUND

Human plasma ATP concentration is reported in many studies as roughly 1000 nmol/L. The present study tested the hypothesis that the measured plasma ATP concentration is lower if ATP release from formed blood elements is inhibited during blood sample processing. A second hypothesis was that pretreatment with aspirin to inhibit platelets would reduce the measured plasma concentration of ATP.

METHODS

Blood was sampled from the antecubital vein in 20 healthy individuals 30 and 60 min after ingestion of aspirin (325 mg) or placebo. Aliquots of each blood sample were added to the usual EDTA/saline solution to inhibit ATP catabolism, or to a new stabilizing solution designed to both stop ATP catabolism and inhibit ATP release from blood elements. The stabilizing solution contained NaCl, EDTA, tricine buffer, KCl, nitrobenzylthioinosine, forskolin, and isobutylmethylxanthine. Plasma ATP was measured with the luciferin-luciferase assay with standard additions in each sample to determine ATP content. Hemoglobin concentration was used as an index of sample hemolysis, and the plasma ATP concentration was corrected for the hemolysis component.

RESULTS

Aspirin pretreatment had no effect on plasma ATP concentrations. However, use of the stabilizing solution resulted in mean (SD) ATP concentrations 8-fold lower than the use of EDTA alone [28 (16) vs 236 (201) nmol/L; P <0.001].

CONCLUSION

When precautions are taken to inhibit ATP release from blood elements during sample preparation, human venous plasma ATP concentration is much lower than previously reported.

Storage of platelets in a new plastic container. Polyvinyl chloride plasticized with butyryl-n-trihexyl citrate

The effect of storage of platelets in a new polyvinyl chloride (PVC) plastic material with a butyryl-n-trihexyl citrate (BTHC) plasticizer (PL 2209) was evaluated. The PL 1240 container, i.e. PVC plastic with a different plasticizer, tri-(ethylhexyl)-tri-mellitate, was used as a reference. Measurements of pH, pO2, pCO2, glucose, lactate, adenosine triphosphate, total adenine nucleotide content, lactate dehydrogenase and platelet factor 4 (PF4) were made during 5 days of storage. Similar results were noted comparing PL 2209 and PL 1240. Differences in pO2 and pCO2 indicate greater gas permeability in PL 2209 than in PL 1240. Significantly higher PF4 levels were found in PL 2209, but the difference could not be attributed to the PL 2209 container itself. Paired autologous reinfusion studies (111Indium) of 6 normal donors gave mean recovery values after 5-day storage of 41.1 +/- 7.4% (PL 2209) and 45.5 +/- 7.7% (PL 1240), t1/2 66 +/- 13 and 75 +/- 5 h, survival time (linear model) 6.3 +/- 1.0 and 6.8 +/- 0.7 and survival time (multiple-hit model) 6.0 +/- 0.7 and 6.5 +/- 0.4 days, respectively. Only the difference in survival time (multiple-hit) was significantly higher in PL 1240. The corrected count increments at 12-24 h following transfusion were 13,300 +/- 10,800 (PL 2209) and 13,600 +/- 11,600 (PL 1240) with no statistically significant difference found. These results indicate PL 2209 as an equivalent alternative to PL 1240 for the 5-day storage of platelets.

Assessment of the NMR visibility of intraerythrocytic sodium by flame photometric and ion-competitive studies

23Na nuclear magnetic resonance (NMR) studies of intraerythrocytic sodium concentrations were performed at 37 degrees C and the accuracy of the method was evaluated through concomitant emission flame photometric analysis. NMR visibility of intraerythrocytic sodium was estimated to be 75 +/- 3%. Verification of the presence of an NMR invisible intraerythrocytic sodium pool and assessment of the mechanisms explaining this invisibility was achieved by measurement of 23Na NMR signal intensities and T1 relaxation times of erythrocyte hemolysate during ion-competitive sodium release from association sites. Signal intensities after addition of small quantities of K+ and Mg2+ to the hemolysates were significantly larger than that expected from dilution of the sample, implying that the additions have resulted in the release of formerly invisible sodium. Furthermore, the intensities following the addition of K+ were significantly larger than those after the addition of Li+ and choline+. This signifies a specificity of the association sites at which sodium has decreased visibility. Increased T1 values following the additions confirmed the release of bound sodium.

Studies on the procurement of blood coagulation factor VIII. In vivo studies on blood components prepared in half-strength citrate anticoagulant

To determine the viability of blood cells collected in half-strength (0.5 CPD.A2) and full-strength citrate anticoagulants, paired crossover autologous survival studies were performed in normal volunteers using 51Cr-labelled red cells after 35 days storage and 111In-labelled platelets after 5 days storage. For both studies, viability was better maintained in 0.5 CPD.A2 anticoagulant. This was significant for red cells (24-hour survival: 80 +/- 6 vs. 52 +/- 21%) but not for platelets by either linear or multiple-hit models (recovery 51 +/- 13 vs. 38 +/- 14%, survival 5.1 +/- 1.4 vs. 3.7 +/- 1.5 days). The poor viability of red cells after storage in full-strength anticoagulant was associated with low cellular adenosine triphosphate levels and was confirmed in follow-up studies.

Studies on the procurement of blood coagulation factor VIII in vitro studies on blood components prepared in half-strength citrate anticoagulant

The effect of replacing a standard citrate anticoagulant with one containing half the amount of citrate on the in vitro properties of components prepared from blood donations was investigated. This resulted in a significant improvement in factor VIII stability such that there was little loss during overnight storage, and this was reflected in the factor VIII yield in cryoprecipitate. The quality of cellular components in red cell units stored up to 35 days or platelet concentrates stored up to 7 days was not adversely affected. Although initial levels were similar to those in standard anticoagulant, the extent of fibrinopeptide A generation and complement C3 breakdown in red cell units stored for 35 days in half-strength citrate was somewhat increased.

Adenine nucleotide concentrations in patients with erythrocyte autoantibodies

Erythrocyte adenine nucleotide concentrations were measured in 154 patients with erythrocyte autoantibodies and 811 normal subjects using a luciferin-luciferase bioluminescent assay. The patients were initially divided into haemolysing and non-haemolysing groups. Red cell adenosine triphosphate (ATP) concentrations were significantly raised in the 96 patients with active haemolysis compared with the normal subjects and with the 58 patients in the non-haemolysing group. Although the patients categorised as non-haemolysing had higher ATP values than the normal subjects, this was because several patients had the anaemia of chronic disorders, which is associated with a shortened red cell life. Measurement of red cell ATP was a useful indicator of mean erythrocyte age and a raised value in patients with erythrocyte autoantibodies reflected active haemolysis.