Effects of platelet-activating factor antagonist E5880 on intrahepatic and systemic metabolic responses to transient hepatic inflow occlusion and reperfusion in the rabbit

We investigated the effects of pretreatment with a potent platelet-activating factor (PAF) receptor antagonist (E5880) on the changes in hepatic and systemic metabolism induced by transient hepatic ischemia and reperfusion. Sixty-five rabbits were assigned to four groups that either did or did not undergo a period of hepatic ischemia and reperfusion with or without pretreatment. E5880 was administered intraportally 1 minute prior to inflow occlusion. Twenty minutes of warm ischemia was followed by 30 minutes of reperfusion. Blood gas analyses and measurements of levels of arterial pyruvate, lactate, and ketone bodies, arterial and portal ammonia and endotoxin, and intrahepatic adenine nucleotide, pyruvate, and lactate were performed. Results were analyzed by either ANOVA or chi-square analysis. Hepatic tissue ATP and energy charge levels were significantly increased and the AMP level was significantly decreased after 30 minutes of reperfusion in the pretreatment group compared to those without pretreatment. At the same time, parameters reflecting hepatic mitochondrial function, such as the arterial ketone body ratio and arterial ammonia level, improved, although they were not statistically significant. No difference was observed for parameters reflecting systemic changes, such as arterial blood gas values and pyruvate and lactate levels. PAF is thought to mediate metabolic changes after hepatic ischemia and reperfusion. PAF released in the liver may exert local effects, which appear to be attenuated by pretreatment with E5880. Systemic metabolic changes seen after hepatic ischemia and reperfusion may be mediated by factors other than PAF.

Effect of trimetazidine on postischemic regional myocardial stunning in the halothane-anesthetized dog

Trimetazidine (TMZ) has been described as a new antiischemic agent. Whereas its precise mechanism of action remains unknown, antioxidant properties and the ability to preserve high-energy phosphate metabolism have been reported. Accordingly, we studied whether TMZ may limit postischemic regional myocardial stunning (known to be caused by reactive oxygen species) and influence recruitment of contractile reserve by inotropic stimulation in a dog model, using halothane to maintain steady anesthesia throughout the experiment. Dogs were submitted to a 15-min coronary artery occlusion followed by reperfusion. The blinded protocol included a 3-day oral pretreatment (1 mg/kg/day), a bolus injection (0.5 mg/kg), followed by intravenous infusion (0.5 mg/h) initiated 15 min before coronary artery occlusion. Despite lower heart rate (HR) and significant reduction of lipid peroxidation in treated dogs, myocardial stunning and recruitment of contractile reserve by dobutamine infusion in the postischemic myocardium were not modified by TMZ. Adenine nucleotide pool in the postischemic myocardium was considerably reduced as compared with the nonischemic myocardium in both groups. Therefore, in halothane-anesthetized dogs, the antioxidant properties of TMZ were not sufficient to protect myocardium in terms of postischemic dysfunction after 15-min ischemia.

[Adenine nucleotide metabolism in acute myocardial infarct and the initiation of free-radical oxidation]

A close relationship between the ADN pool and one of the routes of free radical generation mediated by the xanthine oxidase system has been revealed during studies of changes in adenyl nucleotide metabolism in 140 patients with acute myocardial infarction. The metabolic disorders and changes in the activities of free-radical processes associated with them were found to correlate in patients with different forms of acute myocardial infarction during the acute stage of the disease. The authors consider that this correlation gives grounds for including antioxidative agents in the treatment protocols.

[Energy-dependent processes and metabolism of adenylates in human erythrocytes]

Amphotericin B (1-3 mg/l) decreases the ATP content in erythrocytes by 11-26% and stimulates the K+ efflux but has no effect on the adenylate pool. Adenosine added to the erythrocyte suspension increases the adenylate pool, maintains a high intracellular ATP level for 6-8 hours of incubation at 37 degrees C and diminishes the amphotericin B-induced leakage of K+. Incubation of erythrocytes without glucose for 4-5 hours leads to a 20-50% loss of ATP accompanied by a significant reduction of the adenylate pool. Further addition of glucose partly restores the ATP level. In the presence of adenosine the ATP concentration is restored far more pronounced reaching nearly the original level due to the increase of the adenylate pool.

Alterations in erythrocyte plasma membrane ATPase activity and adenine nucleotide content in a spontaneously diabetic subline of the Chinese hamster

The CHIG/Han subline of the Chinese hamster develops noninsulin-dependent diabetes mellitus characterized by hyperinsulinemia and different degrees of glucose intolerance. To study whether these abnormalities could affect transmembrane cation transport activity, we determined membrane ATPase activity and ATP concentrations in red blood cells of diabetes-resistant CHIA and diabetes-susceptible CHIG sublines of the Chinese hamster. Mg(2+)-ATPase activity was increased in red blood cell membranes of diabetic hamsters compared with that of nondiabetic CHIG and the diabetes-resistant CHIA animals and correlated with plasma triglyceride and cholesterol levels. Ca(2+)-ATPase and Na+/K+ATPase activity were not significantly different between diabetic and nondiabetic hamsters, but for the Na+/K(+)-ATPase, Km was decreased and the Vmax value increased in membrane preparations from severely diabetic hamsters. Both ATP and ADP content were lower in erythrocytes from diabetic than nondiabetic hamsters. Independently of the levels of glycemia, AMP concentrations were higher in CHIG than in CHIA hamsters. While ATP/AMP ratios were found to be decreased in erythrocytes from diabetes-susceptible CHIG hamsters compared to the diabetes-resistant CHIA animals, they were significantly correlated with the levels of glycemia. Furthermore, the relationship between blood glucose levels and kidney weight in hamsters of the diabetes-susceptible CHIG subline was such, that severely hyperglycemic animals displayed the greatest increase in kidney wet weight. These results indicate that the progressive metabolic deterioration in the development of noninsulin-dependent diabetes is associated with significant changes in the activity and kinetic parameters of cellular ATPases which could probably indicate early membrane alterations which may eventually result in the late microangiopathic complications of diabetes.

Physiology and function of platelets from patients with Alzheimer's disease

The discovery that intact Alzheimer amyloid precursor protein is present in platelet granules, has created a great interest in the biochemistry, physiology and function of platelets of patients with Alzheimer disease (AD). In this study we monitored various biochemical and physiological parameters, such as serotonin and adenine nucleotide levels, membrane fluidity, agonist-mediated release of arachidonic acid, thromboxane formation, calcium mobilization, as well as irreversible aggregation and secretion of granule contents. Platelets of patients with AD responded poorly when stirred with weak or potent agonists on a platelet aggregometer. Although capable of agonist-mediated calcium mobilization and synthesis of thromboxanes, the aggregation response of platelets of patients with AD to thrombin and archidonate was considerably compromised. In view of the normal biochemistry and signal transduction capabilities, the compromised response of these cells to potent agonists like thrombin suggested an extrinsic defect. The present study has shown that a plasmatic factor is at least in part responsible for the functional abnormalities of AD platelets.

[Erythrocyte metabolism in meningococcal infection and purulent meningitis]

The red blood cell metabolic parameters ATP, ADP, sigma AN, ATP/ADP, ATP/ATP, energy charge, PAD, 2,3-DPH, Pn were studied in 106 patients with generalized meningococcus infection (GMI) and meningitis of other etiology over their natural history. There was a typical adaptative red blood cell response that featured glycolytic stimulation on hypoxia that ran with impaired red blood cell energy metabolism (RBCEM), negative energy balance. It was the most pronounced at the peak of disease. RBCEM changes occurred in the presence of antioxidative disorders of red blood cells as lowered PAD levels. When early complications, such as shock, brain edema, death developed, there was a high incidence of signs of erythrocytic biochemical disadaptation. The RBCEM changes were associated with the magnitude of cytolysis, i.e. serum AST and AST/ALT levels. The significance of the metabolic changes found in the red blood cells in the pathogenesis and clinical picture of GMI and purulent meningitis is discussed in the paper.

The effects of age on the release of adenine nucleosides and nucleotides from rat caudal artery

1. The spontaneous and alpha-adrenoceptor-induced release of ATP, ADP, AMP and adenosine were determined from arterial segments and from isolated endothelial cells from caudal arteries of young (5-week-old), adult (30-week-old) and old (100- to 110-week-old) Wistar rats. 2. The spontaneous (non-evoked) release of the sum total of the four purines was significantly greater from artery segments of young rats than from adult and old rats. 3. The release of the adenine nucleotides and adenosine induced by methoxamine (10 microM), an alpha 1-adrenoceptor agonist, was greater from artery segments from young rats than from old rats. 4. The spontaneous release of the sum total of the four purines was significantly greater from endothelial cells prepared from caudal arteries of young rats than of old rats. 5. The noradrenaline (10 microM)-induced release of the sum total of the four purines was significantly greater from endothelial cells prepared from caudal arteries of young rats than of old rats. 6. The levels of adenine nucleotides and adenosine, determined in plasma from anaesthetized rats, were significantly higher in young rats compared with adult and old rats. 7. These findings suggest that the release of ATP from the vascular endothelial cells is reduced with advancing age.

Inherited platelet delta-storage pool disease in dogs causing severe bleeding: an animal model for a specific ADP deficiency

The nature of a disorder producing moderate to severe bleeding after minor trauma, venipuncture, and surgery was studied in 3 families of American cocker spaniel dogs. In the 5 affected dogs tested, platelet counts and measurements of plasma coagulant function and von Willebrand factor were normal. However, bleeding times were prolonged in 4 of the 5 affected dogs tested, and platelet aggregation in response to ADP and collagen was consistently abnormal in 3, suggesting that the bleeding disorder was due to abnormal platelet function. Measurements of 14C-serotonin uptake and retention by the affected platelets were normal. However, their ADP content was decreased, while their ATP content was normal, resulting in a mean ATP/ADP ratio of 8.32, compared to a mean ratio of 1.9 in normal canine platelets. Electron microscopy revealed that the number and appearance of the dense granules in the affected platelets were indistinguishable from those of normal controls. These studies suggest that this bleeding disorder results from a deficient delta-granule storage pool of ADP; given the normal serotonin uptake and retention by affected platelets and the apparently normal number of dense granules, the ADP deficiency may be the consequence of a selective defect in delta-granule ADP transport. Additional studies of this unique platelet disorder will provide an opportunity to understand the mechanism of adenine nucleotide storage in platelet delta-granules.

Effects of submaximal physical exercise and immobilization in bed on the adenine nucleotides concentration in human blood platelets

The effects of submaximal physical exercise (75% VO2max) and one month immobilization in bed on the adenine nucleotides concentration in human blood platelets were studied and compared. We have shown that after submaximal exercise and after immobilization in bed the concentrations of adenine nucleotides in blood platelets mainly ATP and ADP were decreased and probably caused by the stimulation of platelet secretory process. Thrombin which stimulated the release of 58.2% +/- 1.5% of total adenine nucleotides from control platelets, liberated decreased amounts of nucleotides from platelets after physical exercise and after immobilization in bed (39.9 +/- 2.1% and 23.6 +/- 2.03% of total, respectively).

Prospective evaluation of interferon-alpha in treatment of chronic active Crohn's disease

Several case reports suggested good effects of interferon-alpha in patients with Crohn's disease. In addition, a decreased production of interferon-alpha in Crohn's disease has been shown in vitro. Treatment with interferon-alpha may activate intestinal natural killer cells and down-regulate the overproduction of inflammatory cytokines like interleukin-6 in Crohn's disease. To evaluate the clinical efficacy of interferon-alpha, we treated 12 patients with a chronic active course of Crohn's disease with recombinant human interferon-alpha prospectively for 24 weeks. Prednisolone was continuously tapered and discontinued at week 12. The end point of the study was the prevention of worsening of clinical symptoms defined with the Crohn's disease activity index and was monitored by acute-phase proteins, interleukin-6 serum concentrations, and endoscopy. The biochemical activity of interferon-alpha was measured by 2',5'-oligo adenylate serum levels. The end point of the study was reached in four patients (33%). In these patients the final Crohn's disease activity index was above 150, which means that they did not achieve clinical remission. All other patients (66%) did not respond to interferon-alpha and had to be withdrawn prematurely. Interferon-alpha did not show any beneficial effect on interleukin-6 or acute-phase protein concentrations and on endoscopic activity. The 2',5'-oligo adenylate levels continuously increased during interferon therapy. Considerable side effects were noted. These results fail to demonstrate a therapeutic role of interferon-alpha in chronic active Crohn's disease.

Breakdown of adenine nucleotides, formation of oxygen free radicals, and early markers of cellular injury in endotoxic shock

OBJECTIVE

To study the influence of shock on muscle and plasma adenine nucleotide and creatine pools and their metabolites, and to identify early markers of cellular injury in shock.

SETTING

Surgical research laboratory, Kuwait and UAE.

DESIGN

Experimental study.

MATERIAL

19 New Zealand rabbits.

INTERVENTIONS

15 rabbits were injected with Escherichia coli endotoxin, and an additional 4 rabbits acted as controls.

MAIN OUTCOME MEASURES

Blood and muscle energy metabolites, platelet count, arterial blood gas tensions, and arterial pressure were followed until the animals died.

RESULTS

Five minutes after injection of endotoxin muscle ATP, creatine phosphate, and total adenine purine concentration decreased. This decrease was later reversed, but again decline to a critical level in the terminal phase. Loss of the muscle creatine pool indicated cellular damage after 3 hours. Plasma hypoxanthine, creatine, and lactate concentrations increased continuously throughout the study.

CONCLUSION

Hypoxanthine formation is a possible source of oxygen free radicals in shock. The rise of hypoxanthine, creatine, and lactate concentrations in plasma during septic shock may reflect early high energy nucleotide failure, membrane injury, and anaerobic metabolism, respectively.

Serum fractions and related agonists with calcium-mobilizing activity in the bovine growth plate chondrocyte

Longitudinal growth of bone involves a complex sequence of cellular events in the cartilaginous epiphysis. Whole blood serum has been shown previously to be a potent stimulus to the cells of the growth plate, as demonstrated by its ability to activate the inositol phosphate-calcium second messenger system, resulting in a rise in intracellular Ca2+. By manipulating the preparation of serum to functionally separate it into its constituent parts, we have shown that the processes of platelet lysis and activation of the clotting cascade are responsible for the generation of factors that stimulate this signaling mechanism in isolated bovine growth plate chondrocytes. Through a subsequent trial of bioactive agents generated in these processes, we identified and partially characterized several novel agonists of growth plate chondrocytes:adenosine triphosphate and adenosine diphosphate, the purine energy substrates, and bradykinin, the bioactive peptide generated in a side reaction of the clotting cascade, each induces a rise in intracellular Ca2+ via release from intracellular ion stores. Additionally, the three distinct isoforms of platelet-derived growth factor (AA, AB, and BB), also released on platelet lysis, were compared with respect to their ability to stimulate the inositol phosphate-calcium second messenger system in growth plate chondrocytes.

Evaluation of a new citrate-acetate-NaCl platelet additive solution for the storage of white cell-reduced platelet concentrates obtained from half-strength CPD pooled buffy coats

BACKGROUND

A new citrate-acetate-NaCl platelet additive solution, identified as PAS 2, was developed to prepare platelet concentrates (PCs) from pooled 0.5 CPD buffy coats (BCs).

STUDY DESIGN AND METHODS

A study was undertaken to evaluate PAS 2 in vitro (n = 8) and in vivo (n = 9) against a commercially available solution (Plasma-Lyte A). In a paired in vitro study, a comparison was made of platelet and white cell concentration; blood gases and bicarbonate; glucose and lactate concentration; total intracellular concentration of adenine nucleotides and beta-thromboglobulin release.

RESULTS

A lower platelet yield (p < 0.0001) and a higher beta-thromboglobulin release (p < 0.01) are observed with Plasma-Lyte A. For this reason, half-strength (0.5) CPD was changed to full-strength CPD in the clinical study with Plasma-Lyte A. In a clinical evaluation of nine patients with bone marrow failure, all received PCs with both PAS 2 and Plasma-Lyte A that had a shelf life of at least 4 days. Corrected count increments (CCls) were as follows, on average (95% Cl): the CCl at 1 to 4 hours was 22.4 (95% Cl, 15.2-29.4) for PAS 2 and 24.0 (95% Cl, 16.9-31.2) for Plasma-Lyte A; that at 12 to 24 hours was 11.3 (95% Cl, 4.1-18.4) for PAS 2 and 14.2 (95% Cl, 7.1-21.3) for Plasma-Lyte A; and that at 36 to 48 hours was 4.2 (95% Cl, -3.0-11.3) for PAS 2 and 8.7 (95% Cl, 1.1-16.2) for Plasma-Lyte A. No significant difference between the two solutions was found.

CONCLUSIONS

PAS 2 and Plasma-Lyte A make important contributions to platelet transfusion quality improvement and give an excellent CCl even after 4 days of storage.

Increase in plasma levels of adenosine and adenine nucleotides after intravenous infusion of buflomedil in humans

To clarify the mode of action of the vasoactive agent buflomedil, we evaluated plasma levels of adenosine and adenine nucleotides after intravenous (i.v.) infusion in humans of 50, 100, and 200 mg of the drug in 20 min. Buflomedil induced an increase of the same order of magnitude in plasma levels of adenosine and adenine nucleotides. Maximal adenosine increase (84%) was observed at the end of the infusion period, whereas peak plasma levels of ATP and ADP (69 and 55%, respectively) and of AMP (61%) were detected 10 and 5 min after discontinuation of infusion, respectively. Although the exact mode of action of buflomedil at the molecular level remains unclear, some indirect findings suggest that the increase in adenosine may be due to enhanced release rather than to inhibition of cell uptake. Because such activity of buflomedil consists of enhancement of physiologic mechanisms of vasodilation and tissue protection occurring in the course of ischemic events, new pharmacologic perspectives for the drug may arise.

Changes in myocardial metabolism and transcardiac electrolytes during simulated ventricular tachycardia: effects of beta-adrenergic blockade

Myocardial ischemia, electrolyte changes, and fluctuations in autonomic tone may play an important role in the presentation of malignant ventricular arrhythmias. beta-Adrenoceptor blocking agents have been shown to decrease the incidence of ventricular fibrillation and sudden cardiac death in patients with coronary artery disease. Therefore we investigated the changes in myocardial metabolism and transcardiac electrolytes during simulated ventricular tachycardia before and after beta-adrenergic blockade. Six patients with normal coronary arteries (group 1) and 12 patients with documented coronary artery disease (group 2) were included in the study. The right ventricle was paced with electrode catheters to a constant cycle length of 400 msec for 3 minutes. Blood samples were withdrawn simultaneously from the coronary sinus and femoral artery to determine the transcardiac differences in metabolic variables and electrolytes before the pacing, at the end of the pacing, and 2 minutes thereafter. After pacing, the patients were given intravenous propranolol (0.15 mg/kg), and the protocol was repeated. Intraarterial blood pressure and electrocardiogram were monitored continuously. There was a rapid decline of the mean arterial blood pressures after initiation of the pacing in both study groups, whereafter the pressures began to rise. Propranolol somewhat blunted the blood pressure recovery, especially in group 2. Norepinephrine levels increased during the pacing in both patient groups, and the increase was accentuated by beta-adrenergic blockade. The femoroarterial coronary sinus difference in lactate turned negative, and pH, PCO2 and potassium differences increased in group 2 during pacing. However, the myocardial energy state remained relatively good as estimated from the nonsignificant change in the transcardiac differences of the plasma adenosine catabolites. There were no changes in the metabolic variables or transcardiac electrolytes in group 1 patients during pacing. Propranolol did not prevent the metabolic ischemia, but it did prevent the pacing-induced decrease in coronary sinus potassium and increase in transcardiac potassium difference. Propranolol also decreased arterial levels of free fatty acids and their extraction in group 2 patients during pacing. In conclusion, blood pressure decay during simulated ventricular tachycardia is followed by instantaneous sympathoadrenergic activation. In patients with coronary artery disease, this process is accompanied by metabolic ischemia and net transfer of extracellular potassium into the intracellular space. The metabolic and electrolyte changes may result in alterations of electrophysiologic millieau, thereby also modifying the clinical characteristics of ventricular tachycardia. Propranolol decreases arterial levels of free fatty acids and prevents changes in transcardiac electrolytes observed in coronary artery disease patients during simulated ventricular tachycardia. These effects of propranolol may be of clinical significance.

Heterogeneity of phenotype in two siblings with adenosine deaminase deficiency

Adenosine deaminase (ADA) deficiency is the cause of about one third of the autosomal recessively inherited cases of severe combined immunodeficiency. Disease severity in ADA deficiency is variable, presumably related in part to heterogeneity in the genotypes causing the disease. We now report on two children in a single family with ADA deficiency who presented with distinct clinical courses. One child presented with severe immunodeficiency and recurrent infections that led to the diagnosis of severe combined immunodeficiency and ADA deficiency at 7 months of age. The older child, who was diagnosed at 3 years of age (after the diagnosis of the younger child), did not have a history of serious or opportunistic infections. Although she was lymphopenic, immune responsiveness was intact, in terms of antibody production, delayed-type hypersensitivity, and in vitro T-cell function. The difference in clinical course in these two siblings is an important observation and demonstrates that the phenotypic expression of ADA deficiency can vary within a family, even in a situation in which protective isolation from infectious pathogens was not a factor in causing the milder course. These observations indicate that expression of disease severity in ADA deficiency may depend to a significant degree on environmental factors and/or on heterogeneity at other genetic loci, which may regulate or modify the expression of the ADA gene or the activity of its product. Furthermore, these observations highlight the importance of recognizing patients with ADA deficiency who present with less severe disease and support the impression that functional immunity in patients with the "late-onset" form of ADA deficiency can deteriorate over time.(ABSTRACT TRUNCATED AT 250 WORDS)

Platelets stored for 6 days in a polyolefin container in a synthetic medium with minimal plasma carry-over

Platelet concentrates (PC) were stored for 6 days in either polyolefin (PO) or polyvinylchloride/di-(2-ethylhexyl)phtalate (PVC/DEHP) bags in 100% plasma or in a synthetic medium with 35 or 10% plasma. For all conditions studied the usual in vitro parameters were well maintained, with a pH above 6.8. In both bag types platelets can be satisfactorily stored for 6 days in a synthetic medium with minimal amounts of residual plasma. For this medium, the PO bag offers a slight advantage with respect to the preservation of platelet ATP content (> 80 versus > 70% in the PVC bags) and aggregation and adhesion capacity. The adhesion capacity increased in the PO bags, while it decreased in the PVC bags.

Variations of adenine nucleotide levels in normal and pathologic human erythrocytes exposed to oxidative stress

Normal human erythrocytes suspended in isotonic saline at 0.5 haematocrit displayed, after 30 min exposure to 1 mM tert-butylhydroperoxide at 37 degrees C, a marked increase of NADPH, while the concentration of the other adenine nucleotides was almost unchanged. Hereditary Spherocytosis and glucose-6-phosphate dehydrogenase-deficient red blood cells exhibited, under basal conditions, higher levels of most of the nucleotides assayed and significant amounts of hypoxanthine. Treatment with tert-butylhydroperoxide caused, in glucose-6-phosphate dehydrogenase-deficient erythrocytes, a pronounced decrease of ADP and of AMP levels, a substantial invariance of other adenine nucleotides and a considerable raise of hypoxanthine. On the contrary, Hereditary Spherocytosis erythrocytes exhibited, after oxidative stress, increased levels of ADP and of AMP, a slight decrease of ATP and an accumulation of hypoxanthine similar to that found in enzyme-deficient red cells. In both the pathologic erythrocytes the addition of phosphate during the oxidative treatment resulted in a lower formation of hypoxanthine, while the presence of 10 mM glucose, fully prevented its appearance.