Dependence of purine loss from human erythrocytes on external pH

Human red cells were incubated at 37 degrees C in physiological saline at pH 7.4 with 8-3H-adenine to label the adenine nucleotides. After washing, the cells were incubated in similar salines which were buffered to different values of pH. The loss of radioactivity from cells into medium was very slow below pH 7.4 and accelerated greatly with increasing pH up to about 7.8. At that pH the loss increased for at least 3 h when it represented more than 30% of the initial radioactivity of the cells. The loss could not be accounted for by haemolysis which remained minimal. The extracellular radioactivity was present mostly in hypoxanthine and some inosine. The loss of purine did not depend on oxygenation of the cells. These results, together with the high-affinity uptake system for adenosine, could provide a partial explanation of the turnover of adenine nucleotide purines of red cells which is many times faster than that of the cells themselves.

Migraine: a platelet disorder

The hypothesis that migraine is caused by a primary abnormality of platelet behaviour was investigated in a total of 77 migraine patients and control subjects. Platelets taken from patients with classical migraine during a headache-free period demonstrated significantly higher spontaneous platelet aggregation and platelet adhesion than platelets from controls. Platelet 5-hydroxytryptamine release within three days of a migraine attack was significantly less than that measured during a migraine-free interval. Platelets from migraine patients differ significantly in their behaviour from normal platelets, and these differences can explain the onset and recurrence of attacks.

[Adenine nucleotide metabolic characteristics in different forms of myocardial infarct]

The "adenosine" and "non-adenosine" mechanisms of adenine nucleotide (ATP, ADP, AMP KP) metabolism were studied in 58 patients with myocardial infarction. Predominant activation of the "adenosine" mechanism of metabolism was revealed in patients with acute myocardial infarction with a marked pain syndrome in the first 24 hours of the disease. In the painless form of myocardial infarction the "nonadenosine" nucleotide metabolism is activated while the "adenosine" type is inhibited. The determination and comparison of indices reflecting the condition of the "adenosine" and "nonadenosine" mechanisms of metabolism provide the possibility for evaluating the severity of the pathological process and, on this basis, elaborating a differentiated approach to the treatment of the patient.

Specimen handling for the assay of adenylates and glycerate 2, 3-bisphosphate in erythrocytes

ATP, ADP, AMP and glycerate 2, 3-bisphosphate in blood are frequently analyzed in order to evaluate erythrocytes for blood donation and to diagnose hemolytic anemias. In order to find an uncomplicated and safe procedure for the preanalytical treatment of blood a freezing-storing procedure using dry ice was worked out and combined with a later PCA precipitation. The pre-freezing stability of the components was also investigated and found to be best at room temperature.

[Regulation of erythrocyte energy metabolism. Dependence of glycolysis characteristics on donor individual parameters]

Approximate analytical expression is obtained for the dependence of erythrocyte glycolytic rate on ATP concentration and donor individual parameters: activation of hexokinase and phosphofructokinase, some kinetic constants and total concentration of adenine nucleotides in the cell.

Radioactive labeling of the adenine nucleotide pool of cells as a method to distinguish among intracellular compartments. Studies on human platelets

The study of adenine nucleotide metabolism is complicated by cellular nucleotide compartmentalization. In platelets, we have been able to use radioactive labeling with adenine to measure, precisely and accurately, changes in the cytoplasmic/mitochondrial pool of adenine nucleotides inspite of the fact that 60% of adenine nucleotides are present in amine-storing granules. High performance liquid chromatography was used to measure the concentrations of ATP, ADP, AMP and IMP from [14C]adenine-labeled platelets under conditions where the granule pool was absent. The radioactive measurements were directly proportional to the chemical measurements. Ethanol-insoluble, actin-bound ADP also had the same specific radioactivity as other metabolic adenine nucleotides. Since this pool can be directly separated from the bulk of cellular nucleotides, its specific radioactivity can be easily measured and used to calculate the concentration of each cytoplasmic adenine nucleotide from its measured radioactivity. These methods may be applicable to other cells.

Reduced platelet sialyltransferase activity in patients with primary release disorder

Platelet sialyltransferase activity was determined in four patients with primary platelet release disorder. Basal enzyme activity was significantly reduced in all. Moreover, enzyme activity in response to stimulation by collagen or sodium arachidonate was also reduced. Platelet total and surface sialic-acid content was normal. The results indicate that defective membrane sialytransferase may be involved in the pathogenesis of primary platelet release disorder.

Phosphorus nuclear magnetic resonance of bovine platelets

31P nuclear magnetic resonance (NMR) spectra of bovine platelets at 28 degrees C display prominent peaks from adenine nucleotides in two different environments, the metabolic and storage pools. Addition of 20 mM 2-deoxy-D-glucose and 0.1 mM 2,4-dinitrophenol depletes metabolic ATP, resulting in loss of nucleotide signals at 5, 10, and 19 ppm and leaving peaks at 6.5, 10.5, and 19 ppm that are assigned primarily to the dense granule storage pool. The ATP/ADP concentration ratio of the remaining pools is 1.9 +/- 0.2, with chemical shifts which reflect a more acidic environment for the intragranular nucleotides than for the cytosol. Isolated bovine dense granules give spectra with similar peak positions to those ascribed to the storage pool after metabolic depletion of whole cells. Storage pool nucleotide spectra are highly temperature dependent. Below 20 degrees C, the beta-ATP peak broadens and decreases in area to the point that it is almost undetectable at 0 degrees C, probably reflecting formation of progressively higher molecular weight aggregates at the lower temperatures. The release reaction was followed by 31P NMR after addition of thrombin at 28 degrees C. Spectra of the cell suspension taken at 5-min intervals were compared to spectra of perchloric acid extracts produced in parallel. A new finding of these experiments is that the released nucleotides rapidly undergo a transition to a "NMR silent" form as part of the bovine platelet release reacton. Metabolic breadkdown and external paramagnetic ion interactions did not explain the loss of signal from the storage pool. During release reaction, the nucleotides may be broadened out beyond detection due to immobilization by divalent cation and/or platelet membrane binding.

Nuclear magnetic resonance studies of blood platelets

Blood platelets contain membrane-enclosed granules which have inside them high concentrations of 5-hydroxytryptamine (serotonin) along with adenine nucleotides and divalent metal ions. 19F n.m.r. of fluorinated serotonin incorporated into the granules of both human and pig intact platelets has shown that the motional state of the serotonin is restricted. Comparison with 31P n.m.r. experiments indicates that this restriction of motion is a consequence of high molecular weight aggregates formed by the adenine nucleotides and metal ions, and that it varies with the species from which the platelets are obtained. In the case of human platelet granules, at least, these high molecular weight aggregates are present in the absence as well as in the presence of serotonin. The biological significance of these data is briefly discussed.

2'5' oligo(A) polymerase activity in serum of mice infected with EMC virus or treated with interferon

Interferon-treated cells show an increase in two double-stranded RNA (dsRNA)-dependent enzymatic activities involving an oligoadenylate polymerase and a protein kinase (ref. 1 and refs therein). The polymerase converts ATP into a series of oligonucleotides characterized by 2'5'-phosphodiester bonds, designated 2'5'-oligo(A) or 2-5A (ref. 1). These oligonucleotides activate an endoribonuclease that degrades RNA in extracts of control and interferon-treated cells. These observations have been made in tissue culture cells and no informatin is yet available on these enzymatic activities in animals with elevated interferon levels. We report here on 2-5A synthesis in tissue homogenates and serum of mice infected with encephalomyocarditis virus (EMCV); this virus induces interferon synthesis when injected intraperitoneally into mice. Significant synthesis of 2-5A was detected in extracts of spleen and lungs, but also, surprisingly, in the serum of these mice. Subsequent experiments showed synthesis of 2-5A in serum of mice treated with the interferon inducer poly(I) x poly(C) (ref. 3) or with mouse fibroblast interferon.

Effects of Pentoxifylline on flap survival

Based on our experimental studies in rats and our clinical experiences, Pentoxifylline appears to have a potential application in the treatment of a skin flap in danger of necrosis. We believe that improving the deformability of red blood cells by increasing ATP content is an important factor in flap survival.

Adenine nucleotides and 2,3-dophosphoglycerate in the erythrocytes during physical exercise and restitution in healthy subjects

The reported investigations were carried out in 6 young (20 years old) healthy males who performed a 10-minute exercise on a Monark cycle ergometer at workloads increasing the heart rate to 170/minute. Before the exercise, after its termination, and after 30 minutes of restitution the concentrations of adenosine-5' triphosphate, adenosine-5' diphosphate, adenosine-5' monophosphate, 2,3-diphosphoglycerate, nicotinamide-adenine dinucleotide and nicotinamide-adenine dinucleotide phosphate were assayed in erythrocytes. After the end of exercise a non-significant increase in ATP concentration and a non-significant decrease of 2,3-DPG were found in the erythrocytes. The concentrations of ADP and AMP were lower than at rest, both, after the end of exercise and after 30 minutes of restitution (p less than 0.05). The concentrations of nicotinamide-adenine dinucleotide and nicotinamide-adenine dinucleotide phosphate decreased after exercise (p less than 0.05) fell even more after 30 minutes of restitution (p less than 0.05).

Extended storage of human platelets at 22 C: changes in glycogen and adenine nucleotide metabolism

The energy metabolism of human platelets stored at 22 C with continuous agitation has been studied. Freshly prepared platelets contain 9.7 mg of glycogen, 9.1 mu moles of ATP, 3.7 mu moles of ADP, 0.9 mu moles of AMP per 10(11) platelets and have an adenylate charge of 0.8. In the first 72 hours of storage there is no appreciable change in the glycogen content, adenylate charge and rate of ATP pool labeling. Therefore, on the basis of these results, the early impairment of function reported by others cannot be ascribed to alterations in the platelet energy metabolism. Upon further storage, however, there is a progressive loss of adenylate and glycogen while hypoxanthine accumulates extracellularly.