THE EFFECTS OF LACTIC-ACID PRODUCTION ON CONTRACTION AND INTRACELLULAR PH DURING HYPOXIA IN CARDIAC-MUSCLE

During hypoxia cardiac contraction declines and there is an intracellu lar acidosis. We find that, if this acidosis is abolished by decreasin g pCO2 there is little restoration of force. Therefore the acidosis is not the major cause of the decline of force. The acidosis may partly result from the generation of lactic acid. No acidosis, is however, se en in isolated cardiac cells. Furthermore a theoretical model shows th at lactic acid production would be expected to produce a transient aci dosis. We suggest that the observed maintained acidosis may be a conse quence of extracellular lactic acid accumulation affecting intracellul ar pH.