Energetics of resting anaerobic frog gastrocnemius at different temperatures by 31P-NMR.

The net rate of phosphocreatine hydrolysis [PCr] [symbol; see text], and tissue pH were determined in anaerobic resting frog (Rana Ridibunda Ridibunda) gastrocnemii by 31-P-NMR in the temperature (T) range from 5 to 30 degrees C. Absolute [PCr] [symbol; see text] values from 0.36 to 10.07 mM/h were estimated assuming a resting [PCr] of 26 mM at 20 degrees C. The corresponding Q10 values ranged from 2.1 (30 degrees C) to 17.5 (5 degrees C). Muscle pH was found to be T-dependent with a 10 degrees C drop in T resulting in an increase of 0.1 pH units. At any given T, pH was found to be constant over a period of at least one hour (30 degrees C) from the onset of anaerobiosis. Based on simultaneous [PCr] [symbol; see text] and pH estimates, the contribution of anaerobic glycolysis ([ATPLA]) to the overall rate of ATP resynthesis ([ATPTot]) was estimated assuming a approximately P/La ratio of 1.2. [ATPTot] was then calculated for each investigated T value as the sum of [PCr] and [ATPLa]. [ATPTot] was found to vary between 5 and 30 degrees C from 0.79 mM/h to 22.15 mM/h. The present study, besides proposing a methodology for the assessment of high energy phosphates hydrolysis by 31P-NMR spectroscopy at changing T, provides a comprehensive analysis of the T-dependence of anaerobic metabolism of the resting anaerobic frog gastrocnemius which may be extrapolated to other tissues.