EFFECT OF METABOLIC-INHIBITORS AND 2ND MESSENGERS UPON NA+-H+ EXCHANGE IN THE SHEEP CARDIAC PURKINJE-FIBER

1. Acid extrusion through Na+-H+ exchange was studied in the sheep cardiac Purkinje fibre (bathed in Hepes-buffered solution, nominally free of CO2-HCO3-) by examining (i) intracellular pH (pH(i)) recovery from an intracellular acid load (induced by 20 mM NH4Cl prepulse) and (ii) the rate of rise of intracellular Na+ activity (a(Na)(i)) following the ammonium prepulse (used as an estimate of apparent Na+ influx on Na+-H+ exchange). The pH(i) and a(Na)(i) were recorded using ion-selective microelectrodes. 2. The pH(i) recovery and rise of a(Na)(i) were both greatly slowed in the presence of 2-deoxyglucose (DOG; glucose-free solution), an inhibitor of glycolysis, indicating inhibition of Na+-H+ exchange.