Nucleoside diphosphate kinase (Ndk) is ubiquitous and highly conserved multifunctional key enzyme in nucleotide metabolism. It generates nucleoside triphosphates (NTPs) by transfer of gamma-phosphates from nucleoside triphosphates such as ATP or GTP to nucleoside diphosphate. The formation of an autophosphorylated enzyme intermediate is involved in that mechanism. The phosphate is usually supplied by ATP and Ndk activity in different subcellular compartments. Ndk may regulate the crucial balance between ATP and GTP or other nucleoside triphosphates. Ndk is playing an important role in bacterial pathogenesis and emerging evidences recognize multiple roles of Ndk in host-microbe interaction. Here, I review some examples of the role of Ndk in intra- and extracellular microorganism.
Adenosine Triphosphate ; Guanosine Triphosphate ; Nucleoside-Diphosphate Kinase

It is clear that creatine plays a reservoir of high energy phosphate bond as creatine phosphate and maintains ATP levels in skeletal muscle and nervous tissues. Creatine and creatine kinase activity are required to utilize creatine phosphate as high energy phosphate. The contents of creatine in testis of rats were determined by the method of Van Pilsum and compared with other organs for the study of the physiological role of creatine in testis. Creatine content of tests was 39.82+/-3.36 ug/g wet tissue compared with skeletal muscle, 52.92+/-10.25 ug/g wet tissue. It was relatively high compared with brain (15.45+/-6.49 ug/g wet tissue), heart (20.0+/-2.91 ug/g wet tissue), kidney (29.55+/-2.52 ug/g wet tissue) and liver (12.68+/-1.94 ug/g wet tissue). Creatinine content of testes (45.84+/-4.08 ug/g wet tissue) was very high, compared with skeletal muscle (24.14+/-7.73 ug/g wet tissue), heart .(23.71+/-4.73 ug/g wet tissue), brain (17.24+/-1.19 ug/g wet tissue), kidney (14.92+/-3.45 ug/g set tissue), and liver (9.59 +/-1.26 ug/g wet tissue). I suppose that creatine in testis of rats may be a part of potent system for generation of ATP from ADP hydrolyzing creatine phosphate.
Adenosine Diphosphate ; Adenosine Triphosphate ; Animals ; Brain ; Creatine Kinase ; Creatine* ; Creatinine ; Heart ; Kidney ; Liver ; Muscle, Skeletal ; Phosphocreatine ; Rats* ; Testis

Adenosine ; metabolism ; Adenosine Kinase ; metabolism ; Adenosine Triphosphate ; metabolism ; Animals ; Brain ; drug effects ; metabolism ; Diet, Carbohydrate-Restricted ; methods ; Diet, Ketogenic ; Energy Metabolism ; Epilepsy ; diet therapy ; metabolism ; Humans

PURPOSE: To investigate the signal enhancement ratio by NOE effect on in vivo 31P MRS in human heart muscle and liver. we also evaluated the enhancement ratios of different phosphorus metabolites, which are important in 31P MRS for each organ. MATERIALS AND METHODS: Ten normal subjects (M: F = 8: 2, age range = 24-32 yrs) were included for in vivo 31P MRS measurements on a 1.5 T whole-body MRI/MRS system using 1H-31P dual tuned surface coil. Two-dimensional Chemical Shift Imaging (2D CSI) pulse sequence for 31P MRS was employed in all 31P MRS measurements. First, 31P MRS performed without NOE effect and then the same 2D CSI data acquisitions were repeated with NOE effect. After postprocessing the MRS raw data in the time domain, the signal enhancements in percent were estimated from the major metabolites. RESULTS: The calculated NOE enhancement for liver 31P MRS were: alpha-ATP (7%), beta- ATP (9%), gamma-ATP (17%), Pi (1%), PDE (19%), and PME (31%). Because there is no creatine kinase activity in liver, PCr signal is absent. For cardiac 31P MRS, whole body coil gave better scout images and thus better localization than surface coil. In 31P cardiac multi-voxel spectra, DPG signal increased from left to right according to the amount of blood included. The calculated enhancement for cardiac 31P MRS were: alpha -ATP (12%), beta-ATP (19%), gamma-ATP (30%), PCr (34%), Pi (20%), PDE (51%), and DPG (72%). CONCLUSION: Our results revealed that the NOE effect was more pronounced in heart muscle than in liver with different coupling to 1H spin system and thus different heteronuclear cross-relaxation.
Adenosine Triphosphate ; Creatine Kinase ; Heart* ; Humans ; Liver* ; Magnetic Resonance Imaging ; Myocardium ; Phosphorus ; Polymerase Chain Reaction

The effects and interactions of 4 beta-phorbol 12,13-dibutyrate(PDB) and polymyxin B(PMB) with adenosine on the electrically-evoked acetylcholine(ACh) release were studied in rat hippocampus. Slices from rat hippocampus were equilibrated with 3H-choline and the release of the labeled product, 3H-ACh, which was evoked by electrical stimulation(3Hz, 2ms, 5Vcm-1, rectangular pulses) was measured. PDB(0.3-10 micorM), a selective protein kinase C(PKC) activator, increased the evoked ACh release in a dose related fashion with an increase in the basal rate of release. The effects of 1(M PDB were significantly inhibited by 0.3 micorM tetrodotoxin(TTX) pretreatment or Ca++-free medium. PMB(0.03-1mg), a selective PKC inhibitor, decreased the ACh release in a dose dependent manner with an increase in the basal rate of release. Adenosine(1-10 micorM) decreased the ACh release without changing the basal rate or release, and this effect was significantly inhibited by 8-cyclopentyl-1,3-dipropylxanthine(2 micorM), a selective A1-receptor antagonist treatment. However, adenosine effects were not affected by PDB and PMB. These results indicate that the PKC play a role in the ACh release in the rat hippocampus but is not involved in the post-receptor mechanism of the A1-adenosine receptor.
Acetylcholine* ; Adenosine ; Animals ; Hippocampus* ; Polymyxin B ; Polymyxins ; Protein Kinase C* ; Protein Kinases* ; Rats* ; Tetrodotoxin

OBJECTIVETo investigate (1) whether ischemic preconditioning (IPC) could protect immature rabbit hearts against ischemia-reperfusion injury and (2) the role of K(ATP) channel in the mechanism of myocardial protection. Since cardioplegia is a traditional and effective cardioprotective measure in clinic, our study is also designed to probe the compatibility between IPC and cardioplegia.

METHODSNew Zealand rabbits aged 14 - 21 days weighing 220 - 280 g were used. The animals were anesthetized and heparinized. The chest was opened and the heart was quickly removed for connection of the aorta via Langendorff's method within 30 s after excision. All hearts were perfused with Krebs-Henseleit buffer balanced with gas mixture (O(2):CO(2) = 95%:5%) at 60 cm H(2)O (perfusion pressure). IPC consisted of 5 min global ischemia plus 10 min reperfusion. Glibenclamide was used as the K(ATP) channel blocker at a concentration of 10 micro mol/L before IPC. Cardiac arrest was induced with 4 degrees C St. Thomas cardioplegic solution, at which point the heart was made globally ischemic by withholding perfusion for 45 min followed by 40 min reperfusion. Thirty immature rabbit hearts were randomly divided into four groups: CON (n = 9) was subjected to ischemia-reperfusion only; IPC (n = 9) underwent IPC and ischemia-reperfusion; Gli (n = 6) was given glibenclamide and ischemia-reperfusion; and Gli + IPC (n = 6) underwent glibenclamide, IPC and ischemia-reperfusion. Coronary flow (CF), HR, left ventricle developed pressure (LVDP), and +/- dp/dt(max) were monitored at equilibration (baseline value) and 5, 10, 20, 30 and 40 min after reperfusion. The values resulting from reperfusion were expressed as a percentage of their baseline values. Arrhythmia quantification, myocardial enzyme in the coronary effluent and myocardial energy metabolism were also determined.

RESULTSThe recovery of CF, HR, LVDP and +/- dp/dt(max) in preconditioned hearts was best among the four groups. The incidence of arrhythmia was low and less CK-MB leaked out in the IPC group. Myocardial ATP content was better preserved by IPC. Pretreatment with glibenclamide completely abolished the myocardial protection provided by IPC, but did not affect ischemia-reperfusion injury.

CONCLUSIONSWhile applying cardioplegia, IPC provides significant cardioprotective effects. Activation of K(ATP) channels is involved in the mechanism of IPC-produced cardioprotection.

Adenosine Triphosphate ; analysis ; Animals ; Creatine Kinase ; secretion ; Creatine Kinase, MB Form ; Heart Arrest, Induced ; Hemodynamics ; Ischemic Preconditioning, Myocardial ; Isoenzymes ; secretion ; Potassium Channels ; physiology ; Rabbits

Adenosine is a naturally occurring breakdown product of adenosine triphosphate and plays an important role in different physiological and pathological conditions. Adenosine also serves as an important trigger in ischemic and remote preconditioning and its release may impart cardioprotection. Exogenous administration of adenosine in the form of adenosine preconditioning may also protect heart from ischemia-reperfusion injury. Endogenous release of adenosine during ischemic/remote preconditioning or exogenous adenosine during pharmacological preconditioning activates adenosine receptors to activate plethora of mechanisms, which either independently or in association with one another may confer cardioprotection during ischemia-reperfusion injury. These mechanisms include activation of K(ATP) channels, an increase in the levels of antioxidant enzymes, functional interaction with opioid receptors; increase in nitric oxide production; decrease in inflammation; activation of transient receptor potential vanilloid (TRPV) channels; activation of kinases such as protein kinase B (Akt), protein kinase C, tyrosine kinase, mitogen activated protein (MAP) kinases such as ERK 1/2, p38 MAP kinases and MAP kinase kinase (MEK 1) MMP. The present review discusses the role and mechanisms involved in adenosine preconditioning-induced cardioprotection.
Adenosine Triphosphate ; Adenosine* ; Heart ; Inflammation ; Mitogen-Activated Protein Kinase Kinases ; Nitric Oxide ; Phosphotransferases ; Protein Kinase C ; Protein-Tyrosine Kinases ; Proto-Oncogene Proteins c-akt ; Receptors, Opioid ; Receptors, Purinergic P1 ; Reperfusion Injury

The atrial acetylcholine-activated K+ (KACh) channel is gated by the pertussis toxin-sensitive inhibitory G (GK) protein. Earlier studies revealed that ATP alone can activate the KACh channel via transphosphorylation mediated by nucleoside-diphosphate kinase (NDPK) in atrial cells of rabbit and guinea pig. This channel can be activated by various agonists and also modulated its function by phosphorylation. ATP-induced KACh channel activation (AIKA) was maintained in the presence of the NDPK inhibitor, suggesting the existence of a mechanism other than NDPK-mediated process. Here we hypothesized the phosphorylation process as another mechanism underlying AIKA and was undertaken to examine what kinase is involved in atrial cells isolated from the rat heart. Single application of 1 mM ATP gradually increased the activity of KACh channels and reached its maximum 40 ~ 50 sec later following adding ATP. AIKA was not completely reduced but maintained by half even in the presence of NDPK inhibitor. Neither ADP nor a non-hydrolyzable ATP analogue, AMP-PNP can cause AIKA, while a non-specific phosphatase, alkaline phosphatase blocked completely AIKA. PKC antagonists such as sphingosine or tamoxifen, completely blocked AIKA, whereas PKC catalytic domain increased AIKA. Taken together, it is suggested that the PKC-mediated phosphorylation is partly involved in AIKA.
Adenosine Diphosphate ; Adenosine Triphosphate ; Adenylyl Imidodiphosphate ; Alkaline Phosphatase ; Animals ; Catalytic Domain ; Guinea Pigs ; Heart ; Nucleoside-Diphosphate Kinase ; Phosphorylation ; Phosphotransferases ; Protein Kinase C* ; Protein Kinases* ; Rats ; Sphingosine ; Tamoxifen ; Whooping Cough

Extracellular ATP (exATP) has been known to be a critical ligand regulating skeletal muscle differentiation and contractibility. ExATP synthesis was greatly increased with the high level of adenylate kinase 1 (AK1) and ATP synthase beta during C2C12 myogenesis. The exATP synthesis was abolished by the knock-down of AK1 but not by that of ATP synthase beta in C2C12 myotubes, suggesting that AK1 is required for exATP synthesis in myotubes. However, membrane-bound AK1beta was not involved in exATP synthesis because its expression level was decreased during myogenesis in spite of its localization in the lipid rafts that contain various kinds of receptors and mediate cell signal transduction, cell migration, and differentiation. Interestingly, cytoplasmic AK1 was secreted from C2C12 myotubes but not from C2C12 myoblasts. Taken together all these data, we can conclude that AK1 secretion is required for the exATP generation in myotubes.
Adenosine Triphosphate/*biosynthesis ; Adenylate Kinase/*metabolism ; Animals ; Cell Line ; Extracellular Space/metabolism ; Isoenzymes/*metabolism ; Mice ; Muscles/cytology/*metabolism

The effect of pinacidil, a K+ channel opener, on the contraction of rabbit carotid artery was investigated by using muscle contraction and Ca2= uptake experiments. Pinacidil reduced phenylephrine-induced contraction by dose dependent manner, which was antagonized by glibenclamide, a blocker of the ATP sensitive K+ channel. Phenylephrine-induced tonic contraction was more reduced by pinacidil than its phasic contraction. In the effect of pinacidil on the Ca2+ uptake of rabbit carotid artery, pinacidil decreased it at the resting state of tissue, dose-dependently. Phenylephrine-induced stimulation of Ca2+ uptake was also reduced by pinacidil. Pinacidil 10micrometer reduced high potassium-induced contraction, which was not reversed by glybenclamide 10micrometer. Threshold concentration of K+ increased by pinacidil pretreatment. Phorbol 12, 13-dibutyrate, an activator of protein kinase C, induced sustained contraction of rabbit carotid artery, which was reduced by pinacidil but not antagonized by glibenclamide. In Ca2+-free buffer, pinacidil also decreased phorbol 12, 13-dibutyrate-induced contraction. These results indicate that pinacidil reduces Ca2+ uptake of vascular smooth muscle by stimulation of K+ channel which could be antagonized by glibenclamide, and another mechanism of vasorelaxation which could not be antagonized by glibenclamide. It was indecated that pinacidil affects the contaction of smooth muscle by the inhibition of protein kinase C.
Adenosine Triphosphate ; Carotid Arteries* ; Glyburide ; Muscle Contraction ; Muscle, Smooth ; Muscle, Smooth, Vascular ; Pinacidil* ; Protein Kinase C ; Vasodilation