Carbohydrate utilization in rat soleus muscle is influenced by carbonic anhydrase III activity

Inhibition of carbonic anhydrase III (CA III; EC 4.2.1.1) activity in type I muscle can influence resistance to fatigue and glycogen utilization. Our aim was to determine if CA III inhibition could influence muscle pH and glycolytic rate. Muscle pH, hexosemonophosphates (HMP), glycolytic intermediates, ATP, and creatine phosphate (CP) were measured at rest and during a fatigue protocol in rat soleus muscles in vitro with or without CA inhibitors (CAI). In resting muscles, CAI resulted in a significant drop in pH (7.11 vs. 7.06, P < 0.05) and in a two- to threefold increase in HMP content compared with control muscles. Measurements of HMP and glycolytic intermediates during the fatigue protocol suggested, however, that the glycolytic flux was not influenced. Globally, muscles incubated with CAI showed larger perturbations of their CP and ATP content than control muscles. The accumulation of HMP induced by the CAI was found to be totally dependent on the combined presence of external glucose and contractile activity, suggesting that inhibiting CA III may augment the responsitivity of the contraction-induced glucose uptake process.