guanosine-triphosphate and Chronic-Disease

Topics: Adenosine Triphosphate; Brain; Brain Chemistry; Brain Diseases; Cell Nucleolus; Cell Nucleus; Chronic Disease; DNA; Guanosine Triphosphate; Humans; Liver Diseases; Microscopy, Electron; Mitosis; Nerve Degeneration; Neuroglia; Portacaval Shunt, Surgical

The mechanism of anti-inflammatory effects of methotrexate (MTX) at low dose may relate to a decrease in availability of the purine precursor or it may depend on accumulation of 5-aminoimidazole-4-carboxamide (AICAR) and the anti-inflammatory nucleoside adenosine. The aim of this study was to evaluate the possible mechanism of action by analysis of changes in blood concentrations of purine and pyrimidine metabolites during MTX treatment.. Venous blood samples were collected from rheumatoid arthritis patients before and at different times for up to 7 days after the start of MTX treatment. Whole blood concentrations of adenosine, uridine, hypoxanthine, uric acid and erythrocyte nucleotides were measured by HPLC.. The initial blood adenosine concentration was 0.073 +/- 0.013 microM and no differences were observed during MTX treatment. However, a decrease in uric acid concentration was observed from 205.5+/-13.5 to 160. 9+/-13.5 microM (P<0.05) within 24 h after MTX administration. The hypoxanthine concentration decreased in parallel with uric acid, while the uridine concentration decreased 48 h after MTX administration. No accumulation of AICAR-triphosphate (ZTP) was observed in the erythrocytes.. MTX decreases circulating purine and pyrimidine concentrations, and their availability for DNA and RNA synthesis, which may affect immune cell proliferation and protein (cytokine) expression. The absence of adenosine concentration changes and lack of ZTP formation is evidence against an AICAR/adenosine mechanism, although localized adenosine concentration changes cannot be excluded.

Topics: Adenosine; Adenosine Triphosphate; Adult; Aminoimidazole Carboxamide; Antirheumatic Agents; Arthritis, Rheumatoid; Chromatography, High Pressure Liquid; Chronic Disease; Cytidine Triphosphate; Erythrocytes; Female; Guanosine Triphosphate; Humans; Hypoxanthine; Methotrexate; Middle Aged; Ribonucleotides; Uric Acid; Uridine

Many fish species adapt to hypoxia by reducing their metabolic rate and increasing hemoglobin-oxygen (Hb-O(2)) affinity. Pilot studies with young broods of cichlids showed that the young could survive severe hypoxia in contrast with the adults. It was therefore hypothesized that early exposure results in improved oxygen transport. This hypothesis was tested using split brood experiments. Broods of Astatoreochromis alluaudi, Haplochromis ishmaeli, and a tilapia hybrid (Oreochromis) were raised either under normoxia (NR; 80-90% air saturation) or hypoxia (HR; 10% air saturation). The activity of the mitochondrial citrate synthase was not different between NR and HR tilapia, but was significantly decreased in HR A. alluaudi and H. ishmaeli, indicating lowered maximum aerobic capacities. On the other hand, hemoglobin and hematocrit levels were significantly higher in all HR fish of the three species, reflecting a physiological adaptation to safeguard oxygen transport capacity. In HR tilapia, intraerythrocytic GTP levels were decreased, suggesting an adaptive increase of blood-O(2) affinity. Similar changes were not found in HR H. ishmaeli. In this species, however, all HR specimens exhibited a distinctly different iso-Hb pattern compared with their NR siblings, which correlated with a higher intrinsic Hb-O(2) affinity in the former. All HR cichlids thus reveal left-shifted Hb-O(2) equilibrium curves, mediated by either decreased allosteric interaction or, in H. ishmaeli, by the production of new hemoglobins. It is concluded that the adaptation to lifelong hypoxia is mainly due to improved oxygen transport.

Topics: Adaptation, Physiological; Adenosine Triphosphate; Animals; Body Weight; Chronic Disease; Cichlids; Energy Metabolism; Erythrocytes; Guanosine Triphosphate; Hematocrit; Hemoglobins; Hydrocortisone; Hydrogen-Ion Concentration; Hypoxia; Isoelectric Focusing; Muscle, Skeletal; Oxygen Consumption; Species Specificity

Norepinephrine (NE)-induced desensitization of the adrenergic receptor pathway may mimic the effects of hypoxia on cardiac adrenoceptors. The mechanisms involved in this desensitization were evaluated in male Wistar rats kept in a hypobaric chamber (380 Torr) and in rats infused with NE (0.3 mg. kg(-1). h(-1)) for 21 days. Because NE treatment resulted in left ventricular (LV) hypertrophy, whereas hypoxia resulted in right (RV) hypertrophy, the selective hypertrophic response of hypoxia and NE was also evaluated. In hypoxia, alpha(1)-adrenergic receptors (AR) density increased by 35%, only in the LV. In NE, alpha(1)-AR density decreased by 43% in the RV. Both hypoxia and NE decreased beta-AR density. No difference was found in receptor apparent affinity. Stimulated maximal activity of adenylate cyclase decreased in both ventricles with hypoxia (LV, 41%; RV, 36%) but only in LV with NE infusion (42%). The functional activities of G(i) and G(s) proteins in cardiac membranes were assessed by incubation with pertussis toxin (PT) and cholera toxin (CT). PT had an important effect in abolishing the decrease in isoproterenol-induced stimulation of adenylate cyclase in hypoxia; however, pretreatment of the NE ventricle cells with PT failed to restore this stimulation. Although CT attenuates the basal activity of adenylate cyclase in the RV and the isoproterenol-stimulated activity in the LV, pretreatment of NE or hypoxic cardiac membranes with CT has a less clear effect on the adenylate cyclase pathway. The present study has demonstrated that 1) NE does not mimic the effects of hypoxia at the cellular level, i.e., hypoxia has specific effects on cardiac adrenergic signaling, and 2) changes in alpha- and beta-adrenergic pathways are chamber specific and may depend on the type of stimulation (hypoxia or adrenergic).

Topics: Adenylate Cyclase Toxin; Adenylyl Cyclases; Adrenergic beta-Agonists; Animals; Cholera Toxin; Chronic Disease; Colforsin; GTP-Binding Proteins; Guanosine Triphosphate; Heart Rate; Heart Ventricles; Hypertrophy, Left Ventricular; Hypertrophy, Right Ventricular; Hypoxia; Isoproterenol; Male; Myocardium; Norepinephrine; Pertussis Toxin; Propanolamines; Protein Kinase C; Rats; Rats, Wistar; Receptors, Adrenergic, alpha-1; Receptors, Adrenergic, beta; Signal Transduction; Sodium Fluoride; Sympathomimetics; Tritium; Virulence Factors, Bordetella; Weight Gain

Intracellular Ca(2+) represents an important trigger for various second-messenger mediated effects. Therefore a stringent control of the intracellular Ca(2+) concentration is necessary to avoid excessive activation of Ca(2+)-dependent processes. Ca(2+)-dependent inactivation of voltage-dependent calcium currents (VCCs) represents an important negative feedback mechanism to limit the influx of Ca(2+) that has been shown to be altered in the kindling model of epilepsy. We therefore investigated the Ca(2+)-dependent inactivation of high-threshold VCCs in dentate granule cells (DGCs) isolated from the hippocampus of patients with drug-refractory temporal lobe epilepsy (TLE) using the patch-clamp method. Ca(2+) currents showed pronounced time-dependent inactivation when no extrinsic Ca(2+) buffer was present in the patch pipette. In addition, in double-pulse experiments, Ca(2+) entry during conditioning prepulses caused a reduction of VCC amplitudes elicited during a subsequent test pulse. Recovery from Ca(2+)-dependent inactivation was slow and only complete after 1 s. Ca(2+)-dependent inactivation could be blocked either by using Ba(2+) as a charge carrier or by including bis-(o-aminophenoxy)-N,N,N',N'-tetraacetic acid (BAPTA) or EGTA in the intracellular solution. The influence of the cytoskeleton on Ca(2+)-dependent inactivation was investigated with agents that stabilize and destabilize microfilaments or microtubules, respectively. From these experiments, we conclude that Ca(2+)-dependent inactivation in human DGCs involves Ca(2+)-dependent destabilization of both microfilaments and microtubules. In addition, the microtubule-dependent pathway is modulated by the intracellular concentration of GTP, with lower concentrations of guanosine triphosphate (GTP) causing increased Ca(2+)-dependent inactivation. Under low-GTP conditions, the amount of Ca(2+)-dependent inactivation was similar to that observed in the kindling model. In summary, Ca(2+)-dependent inactivation was present in patients with TLE and Ammon's horn sclerosis (AHS) and is mediated by the cytoskeleton similar to rat pyramidal neurons. The similarity to the kindling model of epilepsy may suggest the possibility of altered Ca(2+)-dependent inactivation in patients with AHS.

Topics: Adult; Animals; Calcium; Calcium Channels; Chronic Disease; Cytoskeleton; Dentate Gyrus; Disease Models, Animal; Epilepsy, Temporal Lobe; Feedback; Guanosine Triphosphate; Humans; Membrane Potentials; Neurons; Patch-Clamp Techniques; Rats

In the canine basilar artery during chronic vasospasm following subarachnoid hemorrhage, endothelium-dependent relaxations were diminished. Release of endothelium-derived relaxing factor (EDRF), as measured by a bioassay method, was unchanged. Relaxation to nitric oxide (NO) in preparations without endothelium was smaller in the spastic arteries. Production of cyclic GMP, measured by radioimmunoassay, was reduced in the spastic arteries; the impaired production was accompanied by decrease in GTP, the substrate for the production of cyclic nucleotide. The contents of other high-energy phosphates, such as creatine phosphate and ATP were also markedly reduced. Close temporal correlation between the metabolic failure and development of vasospasm was observed. Sarcolemmal regulation of intracellular calcium concentration was impaired in the pathological condition, suggesting a link between the metabolic failure and the pathological protracted contractions. Metabolic changes, and resultant affected viability of smooth muscle cells are likely to be an important factor in the pathogenesis of chronic vasospasm.

Topics: Adenosine Triphosphate; Animals; Basilar Artery; Calcium Channels; Cell Membrane Permeability; Chronic Disease; Cyclic GMP; Dogs; Guanosine Triphosphate; Ischemic Attack, Transient; Muscle Relaxation; Muscle, Smooth, Vascular; Nitric Oxide

High-energy phosphate levels were measured in the canine cerebral artery during chronic vasospasm. Subarachnoid hemorrhage and vasospasm were induced by percutaneous injections of autologous venous blood into the cisterna magna. Narrowing of the artery was confirmed by angiography 7 days later. Levels of adenosine phosphates (adenosine triphosphate (ATP), adenosine diphosphate (ADP), and adenosine monophosphate (AMP)), guanosine phosphates (guanosine triphosphate (GTP) and guanosine diphosphate (GDP)), and creatine phosphate (CrP) in the basilar artery were quantified using high-performance liquid chromatography. The total creatine (Crtotal) content was measured by a spectrophotometric method after acid hydrolysis of CrP. Levels of ATP, GTP, and CrP were markedly reduced in the spastic arteries, and ratios of ATP:ADP, GTP:GDP, and CrP:Crtotal were significantly decreased. The results indicate a serious disturbance in the energy metabolism that takes place in the cerebral artery during chronic vasospasm.

Topics: Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Cerebral Arteries; Chronic Disease; Dogs; Female; Guanosine Diphosphate; Guanosine Triphosphate; Ischemic Attack, Transient; Male; Phosphates; Phosphocreatine; Subarachnoid Hemorrhage

It appeared possible that abnormal purine or pyrimidine metabolism could cause cyclic hematopoiesis by analogy with the defective lymphopoiesis associated with inherited deficiencies of adenosine deaminase and purine nucleoside phosphorylase. Therefore, we examined erythrocyte purine and pyrimidine nucleotide levels, as well as plasma purine and pyrimidine nucleosides and bases in three patients and in normal controls. These studies showed that during neutropenia there was a significant elevation in the levels of guanosine triphosphate (P = 0.005) and adenosine triphosphate (P less than 0.001) in the patients' red cells not attributable to reticulocyte variation. Serial analysis of a patient's plasma showed a fivefold elevation of hypoxanthine (10.6 mumol/L) during neutropenia, with a return to normal values (1.4 mumol/L) as neutrophil numbers increased. Plasma inosine was also significantly elevated in comparison with normal control values (2.0 mumol/L vs. 0.8 mumol/L), whereas plasma and urinary uric acid were within the normal range. Serial analysis of red cells and plasma from two patients with chronic neutropenia showed no elevations of purine or pyrimidine metabolites. These results provide evidence of a link between abnormal concentrations of purine metabolites and cyclic hematopoiesis, and permit the speculation that aberrant purine metabolism is primarily related to the defective hematopoietic cell proliferation that is characteristic of this disease.

Topics: Adenosine Deaminase; Adult; Agranulocytosis; Child; Chromatography, High Pressure Liquid; Chronic Disease; Female; Guanosine Triphosphate; Hematocrit; Hematopoiesis; Humans; Hypoxanthine; Hypoxanthines; Inosine; Male; Neutropenia; Nucleosides; Nucleotides; Purines; Pyrimidines; Uric Acid

Topics: Acute Disease; Alkaline Phosphatase; Aspartate Aminotransferases; Chronic Disease; Female; Guanosine Triphosphate; Hepatitis; Humans; Liver Cirrhosis; Male