[Energy metabolism in gastrocnemius muscles of frogs after tetanic contractions].

The content of the adenylic system components (ATP, ADP, AMP+IMP), creatine phosphate and inorganic phosphorus (Pin) was determined in the frog gastrochemius muscles in vivo and in vitro at different time after one-second and four-second tetanic contractions. After a one-second contraction the content of ATP in the muscles both in vivo and in vitro increases with respect to the initial level and simultaneously the contents of creative phosphate and Pin decrease. 15 seconds after a four-second contraction the content of ATP in the both cases is below the initial level; in the isolated muscles it restores the initial level during the second minute of rest and subsequently does not change significantly. In vivo the content of ATP continues to increase, accounting for 114% of the initial level during the eighth minute of rest. This rise is accompanied by an essential utilization of Pm, the content of which during the eighth minute of rest is 79.4% relative to control. The content of ADP, AMP+IMP after a one-or four-second contraction does not change significantly.