Glycolytic Control Mechanisms: II. KINETICS OF INTERMEDIATE CHANGES DURING THE AEROBIC-ANOXIC TRANSITION IN PERFUSED RAT HEART

Abstract

Abstract The tissue levels of the glycolytic intermediates and adenine nucleotides were measured in perfused rat hearts supplied with 20 mm glucose during the transition from aerobiosis to carbon monoxide-induced anoxia. Facilitation of phosphofructokinase occurred as early as 20 sec after the induction of anoxia at 37°, as shown by an increase of fructose diphosphate and a fall of hexose monophosphate levels. Inorganic phosphate, creatine, adenosine monophosphate, and ADP levels increased simultaneously, while ATP and creatine-phosphate levels decreased. The increases of the nucleotides slightly preceded the rise of fructose diphosphate, and the largest percentage changes were in AMP and inorganic phosphate. These results are in accordance with the postulated activation of phosphofructokinase in vivo by AMP and phosphate. At 25°, the adenine nucleotide changes were much smaller, and an increase of phosphate accounted for the observed activation of phosphofructokinase. Maximum activation of phosphofructokinase occurred between 40 and 60 sec after the onset of anoxia. Overshoots in the levels of many glycolytic intermediates were observed during the transition from the aerobic to the anoxic steady states, indicating a complex sequence of interactions between the various control sites in the glycolytic pathway. Aerobic recovery after a brief period of anoxia was associated with an inhibition of phosphofructokinase, and a return of the levels of high energy phosphate intermediates to their preanoxic values.