EFFECTS OF ADENOSINE ON CARDIAC-PERFORMANCE AND PHOSPHATE-COMPOUNDS IN MICROEMBOLISED GUINEA-PIG HEARTS

Objective: The excessive release of adenosine has been reported to cause hyperaemia and to attenuate ischaemic injury in microembolised hearts. The direct effects of exogenous adenosine on cardiac performance were investigated in microembolised guinea pig hearts with the simultaneous measurement of phosphate compounds. Methods: 21 male guinea pi- hearts were perfused according to the Langendorff technique and microembolism was induced by injecting microspheres. Hearts were then treated as follows: group A, adenosine 20-mu-M and theophylline 60-mu-M; group B, theophylline 60-mu-M; group C, saline (control). Cardiac performance was monitored and phosphate compunds were measured by P-31 magnetic resonance spectroscopy. Results: Group A showed a significant increase in the left ventricular developed pressure and coronary flow, and a modest restoration of ATP content. Pi/(Pi+Pcr) remained virtually constant. There were no significant changes in left ventricular developed pressure or coronary flow in groups B and C. There was a gradual decrease in tissue ATP content and slight increase in Pi/(Pi+Pcr). Conclusions: Adenosine improved cardiac performance without adverse effect on energy metabolism in microembolised hearts. Adenosine also restored the ATP stores in microembolised hearts. (Pi=inorganic phosphate; Pcr=phosphocreatine.)