Phosphate metabolism during muscular contraction in starved frogs (Rana catesbeiana).

1. The muscle tension and the state of high-energy phosphate metabolism during contraction of the sartorius muscle in frogs (Rana catesbeiana) starved for 1-5 months was studied by in vivo 31P-NMR spectrometry. 2. Muscle tension began to decrease after 2-month starvation compared with the control group and decreased to about one-third of the control value after a 5-month starvation. 3. Muscle contraction induced by electrical stimulation or the use of anaerobic perfusion fluid did not decrease the concentration of creatine phosphate (PCr) or beta-ATP, and only negligibly changed the PCr/Pi ratio from starvation. 4. These results suggest a decrease in creatine kinase activity in the muscle of starved frogs.