PRECONDITIONING IN ISOLATED SUPERFUSED HUMAN MUSCLE

Studies in isolated superfused rabbit papillary muscles indicate that preconditioning (PC) is not confined to arterially perfused myocardium . In the present study PC of isolated human right atrial trabeculae wa s investigated avoiding the problems of invasive experimentation in pa tients. Atrial trabeculae were suspended in an organ bath, superfused with Tyrode's solution and field stimulated at 1 Hz. After stabilizati on, muscles were randomly allocated to five groups (n = 8 per group). Control (C) muscles had no additional treatment. PC was induced by 3 m in rapid pacing at 3 Hz with hypoxic. substrate-free buffer, followed by reoxygenation with substrate for 12 min. In two additional groups 8 -p-sulfophenyltheophylline (SPT) was added to the superfusate either d uring stabilization in controls (C + SPT) or during preconditioning (P C + SPT). In the final group, R-phenyl-isopropyl adenosine (R-PLA) was added to the superfusate for 5 min to see whether or not this could s ubstitute for preconditioning. Air muscles were then exposed to 90 min hypo;da with no substrate and pacing at 3 Hz, followed by 120 min reo xygenation at 1 Hz. Recovery of developed tension was significantly im proved by PC (46.5 +/- 2.4% v 24.6 +/- 2.3% in controls) and this prot ective effect was blocked by the addition of SPT without adversely aff ecting controls (recovery in PC + SPT, 25.8 +/- 4.1% and C + SPT, 22.7 +/- 2.9%). R-PVA protected the muscles to a similar extent as PC (43. 8 +/- 1.9%). These data provide evidence for the involvement of adenos ine in preconditioning in human myocardium.