CYTOSOLIC ADENYLATE CHANGES DURING EXERCISE IN PRAWN MUSCLE

P-31 NMR and biochemical analysis were used to assess the effect of heavy exercise on cytosolic adenylate levels in Palaemon serratus abdominal muscle. At rest the MgATP level corresponded to 85.5% of the total ATP content The cytosolic adenylate concentrations of the prawn muscle are considerably different from that of vertebrates The percentage of ADP bound to myofilaments was lower in the prawn muscle. Consequently, the level of free cytosolic AMP was greatly higher (thirtyfold higher) than in vertebrate muscle. During vigorous work, the concentration of MgATP dropped and the cytosolic AMP accumulated, while the cytosolic adenine nucleotide pool decreased significantly. The phosphorylation potential value and the ATP/ADP ratio, calculated from the cytosolic adenylates, dropped acutely during the whole period of muscular contractions. On the contrary, the adenylate energy charge calculated from the cytosolic adenylates decreased slightly. Therefore, even in muscle displaying no AMP deamination, the adenylate charge is stabilized during exercise by the dynamic changes between cytosolic and bound adenylate species.