guanosine-triphosphate and Hypoxia

Pseudomonas aeruginosa encodes many enzymes that are potentially associated with the synthesis or degradation of the widely conserved second messenger cyclic-di-GMP (c-di-GMP). In this study, we show that mutation of rbdA, which encodes a fusion protein consisting of PAS-PAC-GGDEF-EAL multidomains, results in decreased biofilm dispersal. RbdA contains a highly conserved GGDEF domain and EAL domain, which are involved in the synthesis and degradation of c-di-GMP, respectively. However, in vivo and in vitro analyses show that the full-length RbdA protein only displays phosphodiesterase activity, causing c-di-GMP degradation. Further analysis reveals that the GGDEF domain of RbdA plays a role in activating the phosphodiesterase activity of the EAL domain in the presence of GTP. Moreover, we show that deletion of the PAS domain or substitution of the key residues implicated in sensing low-oxygen stress abrogates the functionality of RbdA. Subsequent study showed that RbdA is involved in positive regulation of bacterial motility and production of rhamnolipids, which are associated with biofilm dispersal, and in negative regulation of production of exopolysaccharides, which are required for biofilm formation. These data indicate that the c-di-GMP-degrading regulatory protein RbdA promotes biofilm dispersal through its two-pronged effects on biofilm development, i.e., downregulating biofilm formation and upregulating production of the factors associated with biofilm dispersal.

Topics: Biofilms; Cyclic GMP; Gene Expression Regulation, Bacterial; Glycolipids; Guanosine Triphosphate; Hydrolysis; Hypoxia; Locomotion; Phosphoric Diester Hydrolases; Polysaccharides, Bacterial; Protein Structure, Tertiary; Pseudomonas aeruginosa

Although it is advantageous for hypoxic cells to inhibit protein synthesis and conserve energy, it is also important to translate mRNAs critical for adaptive responses to hypoxic stress. Because internal ribosome entry sites (IRES) have been postulated to mediate this preferential synthesis, we analyzed the 5 '-untranslated regions from a panel of stress-regulated mRNAs for m(7)GTP cap-independent translation and identified putative IRES elements in encephalomyocarditis virus, vascular endothelial growth factor, hypoxia-inducible factors (HIFs) 1alpha and 2alpha, glucose transporter-like protein 1, p57(Kip2), La, BiP, and triose phosphate isomerase transcripts. However, when capped and polyadenylated dicistronic RNAs were synthesized in vitro and transfected into cells, cellular IRES-mediated translation accounted for less than 1% that of the level of cap-dependent translation. Moreover, hypoxic stress failed to activate cap-independent synthesis, indicating that it is unlikely that this is the primary mechanism for the maintenance of the translation of these mRNAs under low O(2). Furthermore, although HIF-1alpha is frequently cited as an example of an mRNA that is preferentially translated, we demonstrate that under different levels and durations of hypoxic stress, changes in newly synthesized HIF-1alpha and beta-actin protein levels mirror alterations in corresponding mRNA abundance. In addition, our data suggest that cyclin-dependent kinase inhibitor p57(Kip2) and vascular endothelial growth factor mRNAs are selectively translated by an IRES-independent mechanism under hypoxic stress.

Topics: Actins; Animals; Binding Sites; Cyclin-Dependent Kinase Inhibitor p57; Glucose; Guanosine Triphosphate; HeLa Cells; Humans; Hypoxia; Mice; NIH 3T3 Cells; Polyribosomes; Ribosomes; RNA, Messenger; Vascular Endothelial Growth Factor A

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

Hypoxic proliferation of pulmonary arterial smooth muscle cells (PASMC) is mitogen dependent, but the signaling pathways mediating hypoxia-induced cell growth are not well understood. We investigated hypoxic proliferation in primary cultures from porcine pulmonary artery smooth muscle. The cells were grown in medium with or without platelet-derived growth factor (PDGF)-B, a potent smooth muscle cell mitogen. Hypoxia induced upregulation of PDGF receptor-beta expression, the primary receptor for PDGF-B. However, PDGF-B-mediated hypoxic enhancement of proliferation was abolished by pertussis toxin, indicating (1) involvement of heterotrimeric Galpha i proteins and (2) minimal effect of increased PDGF receptor expression in hypoxic enhancement of proliferation. We treated PASMC with labeled, nonhydrolyzable analogs of GTP to determine directly if GTP binding proteins were activated by hypoxia in PASMC. We show that hypoxia stimulates GTP incorporation in PASMC both in the presence and absence of PDGF-B. Serum-starved PASMC are able to increase their incorporation of GTP after only 10 min of hypoxia, and this response is not pertussis toxin sensitive. In serum-starved PASMC, we show that hypoxia stimulates incorporation of GTP into a 44-kD protein. The results show that heterotrimeric G proteins are involved in hypoxia-induced signaling in pulmonary vascular smooth muscle cells.

Topics: Animals; Cell Proliferation; Cells, Cultured; Guanosine Triphosphate; Heterotrimeric GTP-Binding Proteins; Hypoxia; Myocytes, Smooth Muscle; Pulmonary Artery; Receptor, Platelet-Derived Growth Factor beta; Signal Transduction; Swine

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

Physiological characteristics of the blood oxygen transport system and muscle metabolism indicate a high dependence on aerobic pathways in the blue gourami, Trichogaster trichopterus. Haemoglobin concentration and haematocrit were modest and the blood oxygen affinity (P50=2.31 kPa at pH 7.4 and 28 degrees C) and its sensitivity to pH (Bohr factor, phi=-0.34) favour oxygen unloading at a relatively high oxygen pressure (PO2). The intracellular buffering capacity (44.0 slykes) and lactate dehydrogenase (LDH) activity (154.3 iu g(-1)) do not support exceptional anaerobic capabilities. Air-breathing frequency in the blue gourami is expected to increase when aquatic oxygen tensions decline. Under threat of predation, however, this behaviour must be modified at a potential cost to aerobic metabolism. We therefore tested the hypothesis that metabolic responses to predatory challenge and aquatic hypoxia are subject to behavioural modulation. Computer-generated visual stimuli consistently reduced air-breathing frequency at 19.95, 6.65 and 3.33 kPa PO2. Bi-directional rates of spontaneous activity were similarly reduced. The metabolic cost of this behaviour was estimated and positively correlated with PO2 but not with visual stimulation thus indicating down-regulation of spontaneous activity rather than breath-holding behaviour. Neither PO2 nor visual stimulation resulted in significant change to muscle lactate and ATP concentrations and confirm that aerobic breath-hold limits were maintained following behavioural modulation of metabolic demands.

Topics: Adaptation, Physiological; Adenosine Diphosphate; Adenosine Triphosphate; Air; Animals; Environment Design; Fishes; Guanosine Triphosphate; Hemoglobins; Hypoxia; L-Lactate Dehydrogenase; Lactates; Muscle, Skeletal; Oxygen; Oxyhemoglobins; Predatory Behavior; Respiration; Stress, Physiological

Ischemic injury to the kidney is characterized in part by nucleotide depletion and tubular cell death in the form of necrosis or apoptosis. Recently, we linked anoxia-induced apoptosis in renal cell cultures specifically to the depletion of GTP. We therefore hypothesized that enhancing GTP repletion in vivo might protect function by reducing apoptosis in postischemic tubules. Male C57 black mice (the "I" group of animals) underwent bilateral renal artery clamp for 32 minutes to induce ischemia and then received either normal saline ("NS") or guanosine ("G"). After 1 hour of reperfusion, renal GTP levels in NS/I were reduced to nearly half of those in sham operated mice, whereas these levels were nearly unchanged in G/I mice. Morphologic examination of tubular injury revealed no significant differences between the two groups. However, there was a significant reduction in the number of apoptotic tubular cells in the medulla in the G/I group as compared with the NS/I group. At 24 hours, creatinine was significantly elevated in the NS/I group, compared to the G/I group. We conclude that guanosine protects against renal ischemic injury by replenishing GTP stores and preventing tubular apoptosis.

Topics: Animals; Apoptosis; Cell Death; Cell Line; Guanosine; Guanosine Triphosphate; Hypoxia; In Situ Nick-End Labeling; Ischemia; Kidney; Male; Mice; Mice, Inbred C57BL; Phenotype; Protein Binding; Reperfusion Injury; Swine; Time Factors

Efficient cellular energy homeostasis is a critical determinant of muscle performance, providing evolutionary advantages responsible for species survival. Phosphotransfer reactions, which couple ATP production and utilization, are thought to play a central role in this process. Here, we provide evidence that genetic disruption of AK1-catalyzed ss-phosphoryl transfer in mice decreases the potential of myofibers to sustain nucleotide ratios despite up-regulation of high-energy phosphoryl flux through glycolytic, guanylate and creatine kinase phosphotransfer pathways. A maintained contractile performance of AK1-deficient muscles was associated with higher ATP turnover rate and larger amounts of ATP consumed per contraction. Metabolic stress further aggravated the energetic cost in AK1(-/-) muscles. Thus, AK1-catalyzed phosphotransfer is essential in the maintenance of cellular energetic economy, enabling skeletal muscle to perform at the lowest metabolic cost.

Topics: Adenine; Adenosine Triphosphate; Adenylate Kinase; Animals; Blotting, Northern; Catalysis; Cloning, Molecular; Creatine Kinase; Embryo, Mammalian; Gene Deletion; Glucose-6-Phosphate; Guanosine Diphosphate; Guanosine Triphosphate; Guanylate Kinases; Hydrogen-Ion Concentration; Hypoxia; Isoenzymes; Magnetic Resonance Spectroscopy; Mice; Mice, Knockout; Mice, Mutant Strains; Muscle, Skeletal; Nucleoside-Phosphate Kinase; Phosphotransferases; Potassium Chloride; Protein Isoforms; Stem Cells; Stress, Physiological; Time Factors; Up-Regulation

Glutamate significantly increased levels of spontaneous chemiluminescence (CL) in rat hippocampal slices incubated under hypoxic conditions. Although it has been previously shown that guanine nucleotides (GN) displace glutamate from several of its receptors, in our study only GMP, as well as the glutamate antagonist MK-801, was able to reverse the increase in CL provoked by glutamate. On the other hand, not only GTP or Gpp(NH)p failed to reverse the action of glutamate, but they increased CL production like glutamate. This effect of GTP/Gpp(NH)p was also reversed by GMP. We concluded that, under neurotoxic conditions, GMP acted as an antagonist and GTP or Gpp(NH)p acted as agonists of glutamate. These results reinforced the evidence of the existence of extracellular site(s) for GN and indicated a possible role for GN in excitotoxicity.

Topics: Animals; Cyclic AMP; Dizocilpine Maleate; Female; Glutamic Acid; Guanine Nucleotides; Guanosine Triphosphate; Guanylyl Imidodiphosphate; Hippocampus; Hypoxia; In Vitro Techniques; Luminescent Measurements; Rats; Rats, Wistar

Patients with tetralogy of Fallot may have episodes of paroxysmal hypoxic spells ("tet spells") or could be asymptomatic. In patients who have these episodes, treatment with a beta-adrenoceptor (betaAR) blocking agent can often ameliorate or attenuate the severity of the symptoms. Additionally, excitement, crying, and situations associated with increased sympathetic activity could provoke the occurrence of these hypoxic spells. We hypothesized that altered myocardial betaAR function may contribute to the development of paroxysmal hypoxic spells in the symptomatic tetralogy patient. Surgically excised right ventricular infundibular myocardial specimens from symptomatic (patients with spells) and asymptomatic patients were used to determine total beta1 and beta2 betaAR density and betaAR adenylyl cyclase activity. Symptomatic patients had a significantly greater number of total betaAR. The relative proportion of beta1 and beta2 receptors was comparable in both patient groups. betaAR-stimulated adenylyl cyclase activity was found to be more enhanced in the symptomatic patient group. Our results indicate that infundibular betaARs may play a role in the development of paroxysmal hypoxic spells.

Topics: Adenylyl Cyclases; Adrenergic beta-Antagonists; Child; Child, Preschool; Colforsin; Female; Guanosine Triphosphate; Heart Ventricles; Humans; Hypoxia; Imidazoles; In Vitro Techniques; Infant; Isoproterenol; Male; Myocardium; Receptors, Adrenergic, beta; Receptors, Adrenergic, beta-1; Receptors, Adrenergic, beta-2; Sodium Fluoride; Tetralogy of Fallot

We used quantitative in situ hybridization and receptor autoradiography to study changes in adenosine receptors following hypoxia-ischemia (H-I) in the neonatal rat brain. Seven-day-old rat pups were subjected to a unilateral ligation of the common carotid artery followed by a 2 h 15 min hypoxic period (7.7% O2 in N2). Adenosine A1 receptor mRNA in cortex and several parts of hippocampus, and A2a mRNA was decreased in the ligated hemisphere 0 h, 1 h and 2 h following hypoxia. The binding of the A1 receptor selective antagonist [3H]8-cyclopentyl-1,3-dipropylxanthine (DPCPX) in the presence or in the absence of GTP decreased immediately after the hypoxic period in both hemispheres and returned thereafter gradually towards control. These results show that there are rapid changes in A1 receptor number on both sides of the brain, and of adenosine A1 and A2a receptor mRNA in the hemisphere that would later develop infarction. Decreases in adenosine receptors may worsen H-I brain damage and have consequences for the use of adenosine directed therapy.

Topics: Animals; Animals, Newborn; Brain; Cerebral Cortex; Down-Regulation; Female; Guanosine Triphosphate; Hippocampus; Hypoxia; Ischemic Attack, Transient; Male; Neurons; Pyramidal Cells; Rats; Rats, Wistar; Receptors, Purinergic P1; Theophylline; Tritium

The stimulation of the formation of inositol phosphate (IP) by (+-)-methyl-2,3,3a,4-tetrahydro-1H-indolo [3,2,1-de] [1,5] naphthyridine-6-carboxylate monohydrochloride (vinconate), a novel indolonaphthyridine derivative, was studied using both cerebral cortical slices and crude synaptic membranes prepared from the rat brain. Vinconate (10 mM-1 mM) inhibited the binding of [3H]quinuclidinyl benzilate to the muscarinic receptor in a dose-dependent manner and the IC50 value for [3H]quinuclidinyl benzilate binding was found to be 17 microM. The rightward shift of the inhibition curve of [3H]quinuclidinyl benzilate binding by carbachol in the presence of GTP (100 microM) was abolished by vinconate (100 microM). Carbachol (10 nM-10 mM) significantly increased [3H]IP formation in a dose-dependent manner and the rate of [3H]IP formation mediated by carbachol stimulation was significantly accentuated in the presence of 10 microM vinconate. The enhancement of [3H]IP accumulation by vinconate was inhibited by approximately 50% in the presence of atropine (1-1000 microM), although up to 1 mM of phentolamine and ketanserin had no effect on the vinconate-induced increase of phosphatidylinositol turnover. Moreover, vinconate significantly accentuated 20 mM KCl-evoked stimulation of [3H]IP formation. Vinconate had no differential effect on the ratio of IP or inositol 1,4-biphosphate and inositol 1,4,5-triphosphate formations. These results suggest that vinconate may induce a facilitation of phosphatidylinositol turnover via the stimulation of muscarinic receptors and a facilitation of coupling between muscarinic receptors and GTP-binding protein. The presence of a direct stimulatory effect of vinconate on phosphatidylinositol turnover has also been suggested.

Topics: Animals; Atropine; Carbachol; Cerebral Cortex; Guanosine Triphosphate; Hypoxia; In Vitro Techniques; Inositol Phosphates; Ketanserin; Male; Phentolamine; Phosphatidylinositols; Potassium; Quinuclidinyl Benzilate; Rats; Rats, Wistar; Receptors, Muscarinic; Synaptic Membranes; Vinca Alkaloids

Neonatal (3-day-old) rat oligodendrocytes grown in monolayer culture and exposed to increasingly hypoxic culture conditions showed a dramatic reduction in myelin basic protein synthesis but no significant inhibition of Tran35S-label incorporation into oligodendrocyte proteins in general or into structural proteins such as actin. However, there was a dramatic increase in synthesis of a novel 22-kDa protein. Reoxygenation of cultures reversed the synthesis of the 22-kDa protein, and thiol and calpain protease inhibitors (EP-459 and leupeptin) did not prevent synthesis of the protein, suggesting that it did not result from proteolysis. The 22-kDa protein (which we have called hypoxin) was coimmunoprecipitated by a polyclonal antibody to actin but did not react with the anti-actin antibody on western blots. The synthesis of hypoxin accounted for up to 50% of the Tran35S-label incorporated into immunoprecipitated protein, suggesting that it plays a major role in the cell's response to hypoxia. Subcellular fractionation revealed that the 22-kDa protein was largely associated with the cytosolic/cytoskeletal compartment. However, it is unlikely to be one of the cytoskeleton-associated Rho or Rac low-molecular-mass (20-24 kDa) GTP-binding proteins because it did not bind [alpha-32P]GTP on western blots. Oligodendrocytes did not synthesize a 22-kDa protein in response to heat shock but did synthesize the typical 70- and 90-kDa heat-shock proteins.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Animals, Newborn; Blotting, Western; Cells, Cultured; Guanosine Triphosphate; Heat-Shock Proteins; Hypoxia; Molecular Weight; Myelin Basic Protein; Nerve Tissue Proteins; Oligodendroglia; Protein Binding; Rats; Rats, Sprague-Dawley; Time Factors

Prostacyclin is a critical mediator of structure and function in the pulmonary circulation, causing both the inhibition of vascular smooth muscle growth and vasodilation via the stimulation of adenylate cyclase. To examine the potential role of alterations in prostacyclin production or mechanism of action in chronic hypoxic pulmonary hypertension, we determined the effects of prolonged (7 d) in vivo hypoxia on in vitro prostacyclin synthesis and mediation of adenylate cyclase activity in rat main pulmonary arteries. In control arteries prostacyclin production exceeded that of prostaglandin (PG) E2 by 25-fold, with 42% originating from the endothelium. Studies utilizing indomethacin revealed that endogenous prostaglandins mediate at least 69% of basal adenylate cyclase activity. Prostacyclin-stimulated enzyme activity was enhanced by exogenous GTP, indicating that this is a receptor-mediated process involving G protein amplification. Comparable dose-related responses to prostacyclin and PGE2 suggest that these agents may activate a common receptor. After 7 d of in vivo hypoxia there was a 2.7-fold increase in in vitro prostacyclin production, with equivalent increases in synthesis in the endothelium and vascular smooth muscle. However, despite this increase there was no change in basal adenylate cyclase activity, and this was associated with attenuated sensitivity of the enzyme to prostacyclin stimulation. Concomitant diminution of the response to beta-adrenergic stimulation, with previously-demonstrated beta receptor downregulation and unaltered postreceptor-mediated activity, suggests that the blunted response to prostacyclin is due to receptor downregulation. Parallel studies of the thoracic aorta indicated that these changes are specific to the pulmonary artery. It is postulated that attenuation of the response of adenylate cyclase to prostacyclin may contribute to the structural changes and hypertension observed in the pulmonary vasculature of the rat with chronic hypoxia.

Topics: Adenylyl Cyclases; Animals; Endothelium, Vascular; Enzyme Activation; Epoprostenol; Guanosine Triphosphate; Hypertension, Pulmonary; Hypoxia; Indomethacin; Isoproterenol; Male; Pulmonary Artery; Rats; Rats, Inbred Strains

We have studied the mechanisms of acute hypoxia tolerance in rainbow trout (Salmo gairdneri). Fish held at 9 degrees C were exposed to various levels of hypoxia for 24 h. At an environmental PO2 of 30 Torr, the fish showed an initial plasma acidosis probably of metabolic origin which was subsequently offset such that blood pH returned to normal within about 4 h. Over this time period, red cell pH was maintained constant. Comparing the effects of different levels of hypoxia following 24 h exposure, oxygen consumption of the animal remained unchanged over a broad range of inspired oxygen tensions but declined by over 30% of normoxic values at inspired water PO2 levels of 80 Torr. This appeared to be a true metabolic depression because signs of increased anaerobic metabolism did not occur until there was a further reduction in water oxygen levels. Rainbow trout appear to be able to maintain a relatively high energy status in their white muscle during 24 h exposure to severe hypoxia (water PO2 = 30 Torr). As the level of hypoxia was intensified, there was a reduction in the oxygen gradient across the gills, probably facilitated in part by the release of catecholamines into the blood. The erythrocytic ATP: Hb4 molar ratios declined with increasing hypoxic stress as did the pH gradient between the erythrocyte and plasma. The overall effect was no change in Hb O2-affinity after 24 h exposure to severe hypoxia.

Topics: Adenosine Triphosphate; Animals; Catecholamines; Guanosine Triphosphate; Hydrogen-Ion Concentration; Hypoxia; Muscles; Oxygen Consumption; Salmonidae; Trout

Topics: Adenine Nucleotides; Aerobiosis; Animals; Coronary Disease; Guanosine Triphosphate; Heart; Hypoxia; Insulin; Male; Muscle Proteins; Myocardium; Perfusion; Phenylalanine; Rats; Tetrodotoxin

Unlike the whole body oxygen affinity, which adapts readily to environmental oxygen tensions, haemoglobins, prepared from normoxic- and hypoxic-accimated eels (Anguilla anguilla) show no adaptive changes in oxygenation properties or in multiplicity. Hypoxic acclimation is, howeveer, accompanied by a strong decrease in red cell nucleoside triphosphates, particularly guanosine triphospphate (GTP), which depresses oxygen affinity of the composite and component haemoglobins more strongly than does the concurring ATP. The effects of pH, temperature and salts on the oxygenation properties of the (isolated) haemoglobins are reported, discussed in relation to the varying environmetal conditions encountered by eels, and compared with data on American and Japanese eels (A. rostrata and A. juponica, respectively.

Topics: Adenosine Triphosphate; Anguilla; Animals; Guanosine Triphosphate; Hemoglobins; Hydrogen-Ion Concentration; Hypoxia; Osmolar Concentration; Oxygen; Phosphates; Temperature

The content of adenine nucleotides in guinea pig seminal vesicles was determined enzymatically. Inosine monophosphate (IMP) was isolated from other tissue nucleotides by two-dimensional thin-layer chromatography on cellulose PEI plates, eluted, and quantitated spectrophotometrically. The intracellular concentration of IMP increased 10-fold over control values (aerobic tissue) concomitantly with the strong ATP drain caused by anoxia. This contrasts markedly with other tissues in which ATP depletion is usually associated with an increase in AMP. Tissue inorganic phosphate also accumulated in an amount corresponding to the apparent ATP depletion. Uric acid did not accumulate. Our data suggest the possibility of a special role for IMP in metabolic control in this tissue.

Topics: Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Chromatography, Thin Layer; Guanosine Triphosphate; Guinea Pigs; Hypoxia; Inosine Nucleotides; Male; Mucous Membrane; Seminal Vesicles; Uric Acid

Topics: Adenine Nucleotides; Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Amino Acids; Animals; Coronary Disease; Guanosine Triphosphate; Hypoxia; Muscle Proteins; Myocardium; Perfusion; Phosphocreatine; Rats

Topics: Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Coronary Disease; Guanosine Triphosphate; Hypoxia; Insulin; Myocardium; Phosphocreatine; Proteins

Topics: Adaptation, Physiological; Adenosine Triphosphate; Animals; Diphosphoglyceric Acids; Eels; Erythrocytes; Guanosine Triphosphate; Hemoglobins; Hypoxia; Isoelectric Point; Nucleotides; Oxygen; Phytic Acid