Synthèse Des Nucléotides Adényliques à Partir De L'adénosine Exogène Dans Le Cœur De Rat Perfusé Dans Des Conditions De Normoxie Et Après Ischémie

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Abstract
The rate of synthesis of myocardial adenine nucleotides from exogenous adenosine was studied in the isolated rat heart perfused under normoxic conditions and following ischaemia. The rate of incorporation of adenosine depended on the extracellular concentration of the precursor, following Michaelis-Menten kinetics with a apparent Km of 51.3 μM and a maximal rate of incorporation of about 1 100 nmol g-1 (wet wt.) 30 min-1. The adenosine uptake induced an increase in ATP concentration (+20%) when the exogenous concentration of precursor exceeded 10 μM. Following low-flow ischaemia (0.5 ml/min, 30 min), the rate of incorporation of 5 μM adenosine was diminished (-23%), but adenine nucleotide level restoration was favoured by the nucleoside administration. After total ischaemia (24 min), the extent of the decrease in adenosine incorporation was the same as in the case of moderate ischaemia but adenine nucleotide content was not restored.