Effect ofP CO2, bicarbonate and lactate on the isometric contractions of isolated soleus muscle of the rat

Summary Isometric contractions of isolated soleus muscles of 3 weeks old rats show a potentiation of the maximal twitch tension when theP _CO2 is increased, or when the [HCO ₃ ^– ] is increased with a reciprocal decrease in [Cl^–]. The reverse response is observed on decrease of theP _CO2 and on decrease of the [HCO ₃ ^– ] with a reciprocal increase in [Cl^–].The addition of lactate ions results in a potentiation of the maximal twitch, whether accompanied by a reciprocal decrease in [HCO ₃ ^– ] or in [Cl^–].The maximal tetanic tension is augmented by rising theP _CO2, by increasing the [HCO ₃ ^– ] with simultaneous lowering of [Cl^–], or by the addition of lactate ions.