Resting metabolism of inorganic phosphorus and changes during mechanical activation in perfused muscle fibres from Balanus.

The levels of inorganic phosphorus (Pi), arginine (and indirectly N-phosphoryl arginine) and adenosine triphosphate (ATP) were measured in intact and perfused muscle fibres from the barnacle Megabalanus psittacus, in resting conditions and during mechanical activity. A twitch caused the liberation of Pi to the intracellular perfusion solution and there was a corresponding decrease in the content of N-phosphoryl arginine of the muscle fibre. Mechanical activation did not induce a significant change in the level of ATP, but since the technique did not allow fast changes in ATP to be observed, the possibility that there was breakdown of ATP followed by a rapid resynthesis cannot be ruled out.