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  • 1
    ISSN: 1432-2013
    Keywords: Na+, K+-ATPase ; Ouabain ; Rubidium ; Vasodilation ; Autoregulation ; Reactive hyperemia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Changes of coronary flow in the isolated perfused spontaneously beating guinea pig heart were induced by elevation of potassium concentration in the perfusion medium (4–16 meq/l). Potassium caused a dose-dependent transient increase of diastolic coronary inflow. The response was inhibited by ouabain (1.4×10−7 M) or reduced temperature. Rubidium ions elicited almost identical vasodilator effects which were also inhibited by ouabain. Autoregulation of coronary flow, reactive hyperemia, and hypoxic coronary dilation were not significantly altered in the presence of ouabain. The results support the hypothesis that potassium as well as rubidium cause vasodilation by activating a Na+, K+-ATPase. On the other hand, they do not favour the view of an essential involvement of potassium ions in local regulation of coronary flow under the conditions studied.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2013
    Keywords: 14C-adenine ; Coronary flow ; Adenosine ; Inosine ; Hypoxanthine ; Hypoxia ; Autoregulation ; Reactive hyperemia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In an attempt to test the hypothesis whether adenosine is involved in the regulation of coronary flow, adenosine, inosine and hypoxanthine were measured in the effluent perfusate and in the tissue of isolated guinea pig hearts under various experimental conditions. In addition, the release of14C-adenosine,14C-inosine and14C-hypoxanthine was determined after prelabeling cardiac adenine nucleotides with14C-adenine. The decrease in coronary resistance induced by hypoxic perfusion (30% and 20% in the gas phase) and during autoregulation was associated with a considerable increase in the release of adenosine, inosine and hypoxanthine. Under both conditions the concentrations of adenosine in the effluent perfusate were clearly within the coronary vasodilating range of exogenously administered adenosine. The tissue content of adenosine also increased significantly when the perfusion pressure was reduced. The release of14C-adenosine closely paralleled the changes in coronary resistance during hypoxic perfusion, autoregulation and during reactive hyperemia. The specific activity of adenosine in the effluent perfusate, however, decreased substantially upon reduction of the oxygen supply to the heart, indicating that the release of14C-adenosine does not provide an absolute measure of total adenosine release by the heart. Our data indicate that the greater part of the adaptive changes of vascular resistance during hypoxia and autoregulation can be attributed to adenosine which is formed at an enhanced rate under these conditions. However, other factors might be involved as well.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-2013
    Keywords: Coronary Dilation ; Adenosine ; Adenine Nucleotides ; Papaverine ; Compound D 600 ; Extracellular Calcium ; Vascular Smooth Muscle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Coronary dilation induced by infusion of adenosine, adenine nucleotides, dipyridamole, and papaverine was quantitated in the spontaneously beating isolated perfused guinea pig heart. Theophylline antagonized the effects of all the substances tested. The inhibition proved to be reversible and of a competitive type. Single injections of ADP and ATP induced flow increases which were more rapid in onset and of greater magnitude than those due to equimolar amounts of adenosine. Lowering the perfusate temperature prolonged coronary responses to ADP and ATP more than those to adenosine. Papaverine produced greater maximal dilation than adenosine. Theophylline inhibited papaverine-induced dilation less effectively than dilating responses to adenosine and other compounds. In the potassium arrested heart, the dilation caused by compound D 600 and papaverine was sensitive to the perfusate calcium concentration but that due to adenosine was unaffected. Dipyridamole, which was equipotent to adenosine in the non-arrested heart, became less potent than adenosine in the arrested heart. The results favour the view that all of the substances tested induce coronary dilation per se and that their effects are not mediated by adenosine. The dilator response to papaverine is assumed to be the result of two effects, one of which is inhibited by theophylline, the other by high extracellular calcium.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 353 (1975), S. 317-326 
    ISSN: 1432-2013
    Keywords: Myocardial Energy Metabolism ; Reactive Hyperemia ; Autoregulation ; Pyruvate ; Adenosine ; Papaverine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Hemodynamic and metabolic characteristics of an isolated guinea pig heart preparation perfused with a pyruvate fortified Krebs-Ringer-bicarbonate solution are described. The preparation is stable for more than 90 min with respect to coronary flow, heart rate, left ventricular pressure,dP/dt, oxygen consumption, and myocardial high energy phosphate levels. The changes in coronary flow induced by alterations of perfusion pressure, ischemia, and hypoxia resemble those seen under in vivo conditions. The preparation also exhibits concentration dependent and reproducible changes in coronary resistance upon administration of adenosine and papaverine. The in vivo like features of this preparation can be mainly attributed to the use of pyruvate as additional and preferentially utilized substrate. The preparation appears to be suitable for quantitative studies of myocardial metabolism and heart function as well as for investigations of the coronary system.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 392 (1982), S. 315-321 
    ISSN: 1432-2013
    Keywords: Acetate ; Metabolites ; Electrolytes ; Exercise hyperemia ; Skeletal muscle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The possible role of acetate in the genesis of exercise hyperemia was studied in five series of dogs. Intraarterial infusion of an isomotic solution of sodium acetate at 0.76 ml/min in the dog forelimb decreased the resistance to flow through skeletal muscle by 48%, primarily by decreasing resistance to flow through small vessels. Skin lymph flow and lymph protein concentration were unaffected. The hindlimb of the conscious dog took up acetate at rest (A-V difference, _58.3±19.6 nmoles/ml) and put out acetate during treadmill exercise (A-V difference, −105.6±20.12 nmoles/ml); femoral venous blood acetate concentration increased by 145 nmoles/ml (control 195 nmoles/ml). In the gracilis muscle of the anesthetized dog, simulated exercise at 0.5, 1.0 or 2.0 Hz increased acetate tissue content (72, 248 and 442 nmoles/g, respectively), output (18,899, and 1,830 nmoles/100 g/min, respectively) and venous cencentration (82, 49 and 39 nmoles/ml, respectively) and changes in tissue acetate content correlated with changes in vascular resistancer=0.75,P〈0.001. Intraarterial infusion of an isosmotic solution of sodium acetate in the quiescent gracilis muscle perfused at constant flow produced a significant (6%) decrease in resistance when arterial blood acetate was increased by a calculated 96 nmoles/ml. These studies suggest that acetate might be included among those metabolites that contribute to exercise hyperemia.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-2568
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Three patients with visceral neuropathy accompanying diabetes mellitus were presented. The manifestations included gastric retention, nausea and vomiting, nocturnal diarrhea, malabsorption, impotence, urinary retention, syncope, and postural hypotension. Physiologic studies demonstrated abnormalities of function of the sympathetic and parasympathetic nervous systems. The resultant disturbances in motility and propulsion appear to account for the gastrointestinal and urinary-tract manifestations, and impairment of the normal sympathoadrenal discharge on standing seems to account for the postural hypotension and syncope.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Digestive diseases and sciences 8 (1963), S. 558-563 
    ISSN: 1573-2568
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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