Measurement of adenine nucleotides in plasma

The goal of this study was to identify the most important variables affecting bioluminescent ATP, ADP and AMP measurements in plasma and to develop an assay that takes these variables into account. Blood samples were drawn from conscious dogs. A 'stop solution' containing EDTA was prepared, which greatly retarded plasma ATP degradation by chelating Mg(+2) and Ca(+2) that are co-factors for many ATPases. Stop solution and blood were mixed using a two-syringe withdrawal system. Samples were centrifuged twice in order to remove red blood cells, and ATP was measured in the supernatant using the firefly luciferase assay. Sample pH was adjusted to the optimal range (7.75-7.95) and Mg(2+) (necessary for the luciferase reaction) was added back to the sample within the luminometer 2 s prior to luciferase addition. Four assay tubes were prepared for each plasma sample, containing standard additions of 0-15 pmol added ATP, in order to quantify native plasma ATP content. In separate plasma/stop solution samples ADP + ATP was measured after converting ADP to ATP via the pyruvate kinase reaction, and AMP + ADP + ATP was measured after addition of both myokinase and pyruvate kinase. Addition of forskolin and isobutylmethylxanthine (IBMX) to the stop solution to inhibit platelets resulted in lower ATP concentrations. Measurement of ATP and haemoglobin from lysed erythrocytes revealed that haemolysis exerts a strong influence on plasma ATP concentration that must be taken into account.

Lack of efficacy of 2-chlorodeoxyadenoside in the treatment of splenic lymphoma with villous lymphocytes

Splenic lymphoma with villous lymphocytes (SLVL) is a B-cell chronic lymphoproliferative disorder. Splenectomy and/or chlorambucil (CLB) are usually regarded as the most effective treatment in SLVL patients. However, a few patients relapse and the second line therapy remains questionable. Although 2-Cda has been evaluated in patients with chronic lymphoid leukemia (CLL) and hairy cell leukemia (HCL), it has been reported as the treatment of SLVL in only one case report. Therefore, we have evaluated its efficacy and toxicity in 7 SLVL patients. The median duration between diagnosis and treatment was 18 months (range, 1 to 59). The patients received 2-CdA (0.1 mg/kg/d) by venous infusion for 7 days with a median number of 1 cycle (range, 1 to 2) either as a first line therapy (one patient) or after a failure of other therapies (splenectomy, chemotherapy). Two patients achieved a complete response. The first one maintained his CR during a follow-up of 9 months and then relapsed; the second patient remained in CR after a follow-up of 20 months. Four patients achieved a partial response and relapsed after a median follow-up of 3.5 months (range, 1 to 4). One patient had no response. The treatment was not well tolerated with many infectious events. In the limits of our study, 2-Cda does not appear to be efficient therapy for SLVL and is not well tolerated for patients in relapse after splenectomy or resistant to CLB.

Use of firefly luciferase in ATP-related assays of biomass, enzymes, and metabolites

The kinetics of ATP reagents not affected by product inhibition or other forms of inactivation of luciferase during the measurement time has been clarified. Under these conditions the decay rate of the light emission expressed as percentage per minute is a measure of luciferase activity and can be given as the rate constant k (min-1), directly reflecting the degradation of ATP in the luciferase reaction. Three types of reagents with different analytical characteristics and different application possibilities have been identified. Stable light-emitting reagents are suitable for measurements of ATP down to 1000 amol. This is the only type of reagent suitable for monitoring ATP-converting reactions, i.e., assays of enzymes or metabolites, assays of oxidative phosphorylation, photophosphorylation, and so on. A higher luciferase activity resulting in a slow decay of the light emission by approximately 10% per minute (k = 0.1 min-1) gives a reagent suitable for measurements down to 10-100 amol. The slow decay of light emission allows use of manual luminometers without reagent dispensers. A further increase of the luciferase activity resulting in a decay rate of approximately 235% per min (k = 2.35 min-1) and only 10% of the light emission remaining after 1 min is suitable for measurements down to 1 amol corresponding to half a bacterial cell. With this type of flash reagent the total light emission can be calculated from two measurements of the light intensity on the decay part of the light emission curve. This new measure is not affected by moderate variations in luciferase activity, but only by changes in quantum yield and self-absorption of the light in the sample. Flash-type reagents require the use of reagent dispensers. The stringent requirements for ATP-free cuvettes, pipette tips, and contamination-free laboratory techniques make it unlikely that flash reagents would be useful in nonlaboratory surroundings. A potential application for this type of reagent is sterility testing. In general, it is concluded that one should select the ideal ATP reagent carefully for each application. Obviously the reagents used in a particular application do not have to match the decay rates given earlier exactly. However, various applications of the ATP technology and the properties of manual and automatic luminometers fall quite nicely into categories corresponding to the properties of the three reagents described. The rapidly growing interest in ATP technology has already resulted in the development of a greater variety of luminometers, from hand-held instruments to high-throughput systems. The continuation of efforts in both reagent and instrument development will undoubtedly result in many new applications.

A luminometric method for the determination of ATP and phosphocreatine in single human skeletal muscle fibres

A sensitive method for the analysis of ATP and phosphocreatine (PCr) in single human skeletal muscle fibres is described. Muscle tissue was freeze-dried and single fibres were dissected free with the aid of low-power microscopy. The fibres were then extracted in trichloroacetic acid and neutralized with KHCO3. The assay is based on the continuous monitoring of light produced as a result of ATP degradation in the firefly luciferase reaction. PCr is measured as the amount of ATP formed in the creatine kinase reaction. The coefficient of variation was less than 4% for both ATP and PCr determination. The amount of tissue required for the assay is approximately 0.5 microgram (dry weight). The assay showed good agreement with spectrophotometric and high-performance liquid chromatographic (HPLC) measurements made upon extracts of whole muscle tissue.

The effect of detergents on firefly luciferase reactions

The reaction rate of ATP-limited firefly luciferase-catalysed reactions, is affected by the presence of detergents. Anionic detergents inhibit luciferase activity without causing significant enzyme inactivation during the reaction. Cationic detergents increase reaction rate several-fold with a sharply defined optimum concentration of detergent for the effect. However, cationic detergents inactivate firefly luciferase during the reaction, resulting in a continuously decreasing reaction rate. Under such conditions, peak light intensity must be used as an indication of initial reaction rate. The inactivation rate increases with increasing detergent concentration. Non-ionic and zwitterionic detergents increase reaction rate over a broad range of detergent concentrations. Enzyme stability during the reaction is not affected by non-ionic detergents and only affected by zwitterionic detergents at high detergent concentration. Cyclodextrins, which can increase reaction rates of some chemiluminescent reactions, have little effect on firefly luciferase activity. Assays for ATP using firefly luciferase must be internally standardized by the constant addition technique in which a known amount of ATP is added to the test sample, since external calibration of such assays, by reference to a previously prepared standard curve, can lead to imprecision when detergents are present.

Methodological problems of direct bioluminescent ATP assay in platelets and erythrocytes

Direct bioluminescent ATP determination in platelets and erythrocytes involves the study of different parameters which are discussed here. Some parameters are linked to the bioluminescent reaction and to the analyte (ATP); others have regard to the biological matrix. The composition of bioluminescent reagents and the preparation and conservation of the ATP standard, also in the presence of excipients, are among the first given. Matrix problems involve cell characteristics related to age and form, lysis resistance and the possible formation of aggregates (platelets) that may inhibit the complete release of ATP. For these reasons we used the most efficient ATP release agent with the lowest inhibitory effect on luciferase. The data obtained correlate well with a bioluminescent method requiring extraction with ethanol/EDTA, and therefore more time, for ATP determination in platelets and erythrocytes.

An in vitro inhibitor of Na-K-ATPase present in an adenosinetriphosphate preparation

An in vitro inhibitor of Na-K-ATPase was discovered in a commonly used preparation of ATP made by the Sigma Chemical Company, St. Louis, Mo. (Sigma grade ATP). As measured by a reliable and widely used assay system in which phosphate liberation in measured colorimetrically, Na-K-ATPase activity in the rat kidney, small intestine and colon was about 50% lower then Sigma grade ATP was used as substrate as compared to another Sigma Chemical Company product II ATP. Mg-ATPase and adenylate cyclase assays were unaffected by substituting Sigma grade for grade II ATP. The inhibitor of Na-K-ATPase could not be identified. Sigma grade ATP probably should not be used when measuring the activity of Na-K-ATPase in the rat kidney, small intestine, or colon.