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OBJECTIVES: This study compared the hyperemic responses to adenosine triphosphate (ATP) administered by intravenous and by intracoronary injection in patients with impaired coronary microcirculation. METHODS: The hyperemic responses to intravenous and intracoronary administration of ATP in 107 patients (mean age 63 +/- 10 years, 77 males, 30 females) with impaired coronary circulation [including myocardial infarction (n = 68), cardiomyopath (n = 20) and diabetes mellitus (n = 11)] were compared by measurement of coronary flow reserve (CFR) using the Doppler guide wire. Patients with chest pain syndrome were used as the normal controls. The coronary blood flow velocity was measured at rest and during peak hyperemic responses to intravenous infusion (150 micrograms/kg/min) and intracoronary infusion of ATP (50 micrograms in the left coronary artery, 25 micrograms in the right coronary artery). The CFR was calculated as the ratio of averaged peak velocity during hyperemia to baseline averaged peak velocity. RESULTS: The CFR after intravenous administration of ATP (CFRi.v.) was well correlated with CFR by intracoronary administration of ATP(CFRic) (r = 0.77, p < 0.001). However, the CFRi.v. was also inversely correlated with the ratio of CFRic to CFRiv (CFRic/i.v.) (r = -0.36, p < 0.001). There were no relationships between the changes of hemodynamic parameters(blood pressure and heart rate) induced by ATP and CFRic/i.v. A lower CFRi.v. of less than 2.0 provided significantly greater CFRic/i.v. than that of CFRiv greater than 2.0. CONCLUSIONS: The maximal hyperemic response of coronary artery was not always induced by conventional intravenous administration of ATP, especially in patients with lower CFR than 2.0. High dose of intravenous ATP and/or intracoronary ATP should be administered in patients with lower CFR to attain maximum hyperemia in the impaired coronary circulation.
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PURPOSE: We compared the potency of adenosine triphosphate (ATP) and its nonhydrolyzable analogue alpha,beta-methylene ATP for generating contractions in human detrusor smooth muscle from patients with a stable, unstable and obstructed bladders. The different ATP potencies were compared with the ecto-adenosine triphosphatase (ATPase) of these samples. MATERIALS AND METHODS: Contractile experiments were done in vitro by superfusing samples with purines and dose-response curves were generated. Ecto-ATPase activity was measured from the rate of ATP hydrolysis sensitive to the ecto-ATPase inhibitor ARL 67156 with a luciferin-luciferase assay. RESULTS: ATP generated contractions with a mean EC50 of 933 microM. in tissue from stable bladders and was significantly more potent in tissue from unstable and obstructed bladders (EC50 141 and 172 microM., respectively). alpha,beta-methylene ATP was more potent in tissue from stable and unstable bladders (mean combined EC50 3 microM.). In guinea pig detrusor the mean EC50 for ATP and alpha,beta-methylene ATP was 138 and 5.5 microM., respectively. Mean total ATPase activity in unstable bladder biopsies plus or minus standard deviation was about 50% of that in stable bladder biopsies (2.54 +/- 1.50 versus 1.37 +/- 0.46 nmol. per second per mg. protein ). The ARL 67156 sensitive fraction was also significantly less in samples from unstable compared with stable bladders (mean 0.94 +/- 0.41 versus 0.36 +/- 0.26 nmol. per second mg. protein ). CONCLUSIONS: The greater potency of ATP for generating contractions in detrusor from unstable bladders may be due to reduced extracellular hydrolysis, allowing purine greater access to detrusor smooth muscle. This finding may explain atropine resistant purine based contractions in detrusor from unstable bladders.
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Adenosine triphosphate and pyrophosphate prevent the loss of Ca(//)-activated adenosine triphosphatase activity caused by high concentrations of mercurial sulfhydryl reagent. They concomitantly prevent the transformation of myosin into faster-sedimenting products. This is adduced as support for the hypothesis that the strategic sulfhydryl group is not binding adenosine triphosphate at the active site, but is initiating a conformational change upon its reaction with the mercurial reagent.
Adenosine triphosphate (ATP) and uridine triphosphate (UTP) receptors were studied by comparing the contractile responses to UTP with those to ATP in the rat tail and femoral arteries and dog saphenous vein, after endothelium removal confirmed by histology, and near abolition of relaxation to acetylcholine. Contractions induced by ATP and UTP were dose dependent, as assessed from preparations at resting tension. Contraction curves were very different: rapid subsidence with ATP and sustained contraction with UTP. In the rat tail artery and the dog saphenous vein, quinidine, nordihydroguaiaretic acid (NDGA) and phentolamine inhibited the contractions induced by ATP, whereas those induced by UTP were only slightly reduced in the presence of NDGA and were not antagonized by quinidine and phentolamine. In all three vessels, alpha-beta methylene ATP induced desensitization to ATP, whereas it did not antagonize the UTP-induced contractions. Reactive blue 2 was incapable of antagonizing contractions to ATP and UTP in these preparations. In addition, UTP-induced contractions were hardly inhibited in a calcium-free Krebs solution, whereas ATP was totally inhibited. We showed that a calcium antagonist, nicardipine, was more potent on the UTP-induced than on the ATP-induced contractions. These results showed the UTP-induced contraction to be mediated by a new class of receptors, qualified here as 'pyrimidinoceptors', for which no antagonist is known. These results were obtained in the tail and femoral arteries of the rat and from the dog saphenous vein. ATP induced contraction in these three vessels via P2x purinoceptors. P2x purinoceptors and 'pyrimidinoceptors' are localized on the vascular smooth muscle.
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The release of iron from transferrin was investigated by incubating the diferric protein in the presence of potential iron-releasing agents. The effective chemical group appears to be pyrophosphate, which is present in blood cells as nucleoside di- and triphosphates, notably adenosine triphosphate (ATP). An alternative structure with comparable activity is represented by 2,3-diphosphoglycerate. Neither 1 mM adenosine monophosphate (AMP) nor 1 mM orthophosphate released iron from transferrin. The ATP-induced iron-releasing activity was dependent on weak acidic conditions and was sensitive to temperature and sodium chloride concentration. The rate of iron release rapidly increased as transferrin was titrated with HCl from pH 6.8 to 6.1 in the presence of 1 mM ATP and 160 mM NaCl at 20 degrees C. Iron release from transferrin without ATP was observed below pH 5.5. Ascorbate (10(-4) M) reduced Fe(III), but only after iron release from transferrin by a physiological concentration of ATP. A proposal for the mechanism of iron release from transferrin by ATP and the utilization of reduced iron by erythroid cells is described.
1 In citrated platelet-rich plasma, freshly prepared from rabbit blood, the velocity of platelet aggregation was within limits proportional to the log of the concentration of added adenosine diphosphate (ADP). 2 Addition of either adenosine triphosphate (ATP) or its beta,y-methylene analogue inhibited aggregation similarly except that the analogue was about half as potent as ATP. beta,y-Methylene ATP also reversed the optical effects associated with the shape change of platelets very similarly to ATP itself. 3 As beta,y-methylene ATP is not a substrate for nucleoside diphosphokinase, these observations do not support the proposition that inhibition of aggregation by added ATP is due to its utilization by the nucleoside diphosphokinase of platelets.
An adenosine triphosphate-stimulated deoxyribonuclease was purified to about 4200 fold from Bacillus cereus. The enzyme activity of the crude extract increased by a factor of about 5 after dialysis. One of the low molecular weight inhibitors of the crude extract was found to be inorganic phosphate. During enzyme purification two nucleases were identified. One of them was specific to denatured DNA and the other one degraded both denatured DNA and native DNA. The activity towards native DNA could be increased several times by ATP. Through all steps of purification the ATP-independent DNase always accompanied the ATP-dependent one and the ratio of their activity was found to be constant. The ATP-dependent DNase also possessed ATPase activity stimulated both by native and denatured DNA. The fact that ATPase was stimulated by DNA and went together with ATP-dependent DNase during purification suggests that these functions belong to the same enzyme complex. Maximal activity of ATPase had broader pH, Mg2+ and ATP concentration ranges than that of DNase. Cooperation of the two functions may be limited only to a narrow range of ATP concentration. Km for ATPase was 1.6x10-4 M ATP.
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Adenosine triphosphate (ATP) hydrolysis catalyzed by the plasma membrane (Na+,K+)ATPase isolated from several sources was inhibited by Mg+, provided that K+ and ATP were also present. Phosphorylation of the adenosine triphosphatase (ATPase) by ATP and by inorganic phosphate was also inhibited, as was p-nitrophenyl phosphatase activity. (Ethylenedinitrilo)tetraacetic acid (EDTA) and catecholamines protected from and reversed the inhibition of ATP hydrolysis by Mg2+, K+ and ATP. EDTA was protected by chelation of Mg2+ but catecholamines acted by some other mechanism. The specificities of various nucleotides as inhibitors (in conjunction with Mg2+ and K+) and as substrates for the (Na+, K+) ATPase were strikingly different. ATP, ADP, beta,gamma-CH2-ATP and alpha,beta-CH2-ADP were active as inhibitors, whereas inosine, cytidine, uridine, and guanosine triphosphates (ITP, CTP, UTP, and GTP) and adenosine monophosphate (AMP) were not. On the other hand, ATP and CTP were substrates and beta,gamma-NH-ATP was a competitive inhibitor of ATP hydrolysis, but not an inhibitor in conjunction with Mg2+ and K+. The Ca2+-ATPase from sarcoplasmic reticulum and F1, the Mg2+-ATPase from the inner mitochondrial membrane, were also inhibited by Mg2+. Catecholamines reversed inhibition of the Ca2+-ATPase, but not that of F1.
Adenosine triphosphate (ATP) not only functions as an energy-carrier substance and an informative molecule, but also acts as a marker substance in studies of both bio-traces and cellular/tissular viability. Due to the importance of the ATP function for living organisms, in situ assays of ATP are in demand in various fields, e.g., hygiene. In the present study, we developed an ATP sensor that combines the selective catalytic activity of enzyme and the properties of an ion selective field effect transistor (ISFET). In this system, the ATP hydrolyrase, "apyrase (EC 3.6.1.5.)" is encased in a gel and mounted on a Ta(2)O(5) ISFET gate surface. When the enzyme layer selectively catalyzes the dephosphorylation of ATP, protons are accumulated at the gate because the enzymatic reaction produces H(+) as a byproduct. Based on the interfacial enzymatic reaction, the response from the ISFET is completely dependent upon the ATP concentration in the bulk solution. This device is readily applicable to practical in situ ATP measurement, e.g. hygienic usage.
Adenosine triphosphate (ATP) has been shown to be an inhibitory or a stimulatory agent for cell growth in various types of cells. Here, we studied the effects of extracellular ATP on two pancreatic cancer cell lines, PK-1 and YAPC established by us. In both cell lines, ATP inhibited cell growth in a time- and dose-dependent manner, whereas the same doses of ATP stimulated DNA synthesis. Flow cytometric analysis of the cells incubated with or without ATP demonstrated the ATP-induced striking increase in cells at S-phase. The same analysis showed also the increase in sub-G0/G1 population in the same analysis and the electrophoretic pattern of DNA showed the occurrence of ATP-induced cell disintegration likely to be apoptosis. We suggest that extracellular ATP is cytotoxic for pancreatic cancer cells because of its induction of cell cycle arrest at S-phase and cell death, possibly apoptosis, overcoming the promotion of the entry into S-phase.