31P-NMR studies of phosphate metabolites in intact red and white swimming muscles of cod ( Gadus morhua L.)

Abstract

1. 1. 31P-NMR was used to characterise intracellular phosphate pools and their post mortem changes at 7°C in intact red and white cod muscles under anaerobic conditions. 2. 2. A total phosphate content of 55 and 60 mM was observed in red and white muscle, respectively. The concentration of P-creatine was 14 mM in the white and 9 mM in the red muscle, while that of inorganic phosphate, P i (30 mM), ATP (9 mM), and sugar phosphate (5 mM) were similar in both muscles. 3. 3. During the first 90 min after death, the decrease in P-creatine showed a first order breakdown with a concomitant stoichiometric increase in P i content, whereas the ATP and sugar phosphate remained the same. The intracellular pH decreased from 7.4 to 7.3 in this period. 4. 4. The steady-state rate constant of myosin ATPase was 0.0054 and 0.0022/min for red and white muscles, respectively. 5. 5. Individuals kept under diminished oxygen tension prior to being killed, showed a reduced P-creatine level in both muscles.