Adenosine 5 -diphosphate-stimulated

Dismption of the endothehal surface of blood vessels expose coUagen fibers and connective tissue. These provide surfaces that promote platelet adherence, platelet release reaction, and subsequent platelet aggregation. Substances Hberated from the platelets stimulate further platelet aggregation, eg, adenosine diphosphate maintain vasoconstriction, eg, serotonin and participate in blood coagulation, eg, platelet Factors III and IV. In addition, the release reaction modifies platelet membranes in a manner that renders phosphoHpid available for coagulation. The thrombin [9002-04-4] elaborated by the coagulation mechanism is a potent agent in the induction of the platelet release reaction. 

Ribeiro JA, Walker J (1975) The effects of adenosine triphosphate and adenosine diphosphate on transmission at the rat and frog neuromuscular junctions. Br J Pharmacol 54 213-18 Ribeiro JA, Sa-Almeida AM, Namorado JM (1979) Adenosine and adenosine triphosphate decrease 45Ca uptake by synaptosomes stimulated by potassium. Biochem Pharmacol 28 1297-1300... 

Adenosine, in addition to serving as a substrate for the generation of cAMP plays a physiologic role as a platelet inhibitor and a vasodilator and may attenuate neutrophil-mediated damage to endothelial cells, Adenosine diphosphate (ADP)— a potent platelet agonist—is converted to adenosine, which is taken up rapidly by cells, especially erythrocytes and endothelial cells, A small proportion is metabolized to the aforementioned cyclic nucleotides. The remainder is broken down to inosine and subsequently to xanthine. Dipyridamole inhibits the active transport of adenosine into cells, but does not interfere with the passive diffusion. Since the platelet inhibitory effects of adenosine proceed via stimulation of adenylate cyclase, these effects can also be amplified by dipyridamole, In circulating blood, the largest amount of adenosine is found in red blood cells, This may, in part, help explain why dipyridamole is much more effective in whole blood than in plasma. 

All interactions between UFH and platelets are complex and only partially elucidated, but it is known that heparin itself stimulates platelets via a platelet-binding domain of heparin (14). In the therapeutic range, UFH induces the release of P-selectin and activates GPIIb/llla receptors when adenosine diphosphate (ADP) or thrombin receptor agonist peptide stimulates platelet responsibility, and then enhances platelet aggregation (15,16). Even in healthy individuals, agonist-induced platelet aggregation is often enhanced when heparin is added. 

The enzyme has been isolated from many tissues, the best source being a heart muscle or yeast. The isocitrate dehydrogenase requires the presence of cofactors Mg2+ or Mn2+. As an allosteric enzyme, it is regulated by a number of modulators. ADP, adenosine diphosphate, is a positive modulator and therefore stimulates enzyme activity. The... 

Chlorophenols block adenosine triphosphate (ATP) production, without blocking the electron transport chain. They inhibit oxidative phosphorylation, which increases basal metabolic rate and increases body temperature. As body temperature rises, heat-dissipating mechanisms are overcome and metabolism is accelerated. Adenosine diphosphate (ADP) and other substrates accumulate, and stimulate the electron transport chain further. This process demands more oxygen in a futile effort to produce ATP. Oxygen demand quickly surpasses oxygen supply and energy reserves of the body become depleted. 

Aune and Pogue344 presented data indicating that at least two distinct mechanisms, (1) stimulation of cellular catabolism of tryptophan and (2) stimulation of cellular catabolism of nicotinamide adenine dinucleotide (NAD) by adenosine diphosphate-ritosyl transferase (ADP-RT), can account for IFN-y-mediated inhibition of tumor cell growth. Both mechanisms appear to be sensitive to oxygen tension and to changes in intracellular glutathione concentrations, and both mechanisms lead to loss of intracellular NAD. 

No effects in isolated mitochondrial preparations on state 4 respiration, ADP-stimulated or 2,4-dinitrophenol-stimulated respiration, the respiratory control ratio, the adenosine diphosphate/oxygen ratio, the rate of calcium-induced mitochondrial swelling at 50 pM. Loss of MMP was seen rally at the highest concentration of ximelagatrtm tested, 300 pM, in mitochondria exposed for 24 h. No effects on P-oxidation of fatty acids up to 300 pM... 

One mechanism that has been proposed to explain the hepatotoxicity of 1,1,2-trichloroethane is the generation of free radical intermediates from reactive metabolites of 1,1,2-trichloroethane (acyl chlorides). Free radicals may stimulate lipid peroxidation which, in turn, may induce liver injury (Albano et al. 1985). However, Klaassen and Plaa (1969) found no evidence of lipid peroxidation in rats given near-lethal doses of 1,1,2-trichloroethane by intraperitoneal injection. Takano and Miyazaki (1982) determined that 1,1,2-trichloroethane inhibits intracellular respiration by blocking the electron transport system from reduced nicotinamide adenine dinucleotide (NADH) to coenzyme Q (CoQ), which would deprive the cell of energy required to phosphorylate adenosine diphosphate (ADP) and thereby lead to depletion of energy stores. 

When the actinomyocin filaments of the muscles are caused to move in response to neural stimulation, ATP reserves are rapidly used, and ATP becomes adenosine diphosphate (ADP), a compound with much less energy density than ATP. Maximally contracting mammalian muscle uses approximately 1.7 x 10 mole of ATP per gram per second (White et al., 1959]. ATP stores in skeletal muscle tissue amount to 5 X 10 mole per gram of tissue, or enough to meet muscle energy demands for no more than 0.5 sec. 

Zingarelli B, O Connor M, Wong H et al. Peroxynitrite-mediated DNA strand breakage activates poly-adenosine diphosphate ribosyl synthetase and causes cellular eneigy depletion in macrophages stimulated with bacterial lipopolysaccharide. J Immunol 1996 156 350-8. 

Miller EG (1975) Stimulation of nuclear poly (adenosine diphosphate-ribose) polymerase activity from HeLa cells by endonucleases. Biochim Biophys Acta 395 191-200... 

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