EFFECTS OF BERAPROST ON THE TRANSMEMBRANE POTENTIALS OF GUINEA-PIG VENTRICULAR MUSCLES DURING NORMOXIA AND HYPOXIA-REOXYGENATION

1 The present study was performed to determine whether beraprost, a ne w stable analogue of prostacyclin, may exert beneficial effects on the transmembrane action potentials during normoxia and hypoxia-reoxygena tion in isolated right ventricular muscles of the guinea-pig. 2 Under normal oxygenation, beraprost (0.01-100 mumol-1) had no effects on the electrophysiological parameters. 3 Hypoxic conditions induced a decre ase in action potential duration (APD) without affecting other action potential parameters. Beraprost inhibited this hypoxia-induced decreas e in APD. However, beraprost had no effect on the decrease in contract ile force induced by hypoxia, whereas it significantly improved the re covery of contractile force after reoxygenation. 4 Pinacidil-induced s hortening of APD was not antagonized by beraprost. 5 Hypoxia significa ntly decreased the myocardial adenosine triphosphate (ATP) level, whic h was also prevented by beraprost. 6 These results suggested that bera prost may inhibit the hypoxia-induced shortening of APD by some mechan isms which contribute to the maintenance of muscle ATP level.