Nuclear magnetic resonance studies of sodium ions in isolated frog muscle and liver.

Nuclear magnetic resonance (NMR) was used to determine Na(+) complexing in muscle and liver (at 23 degrees C) from bullfrogs (Rana catesbeiana) and to study the influence of temperature on Na(+) complexing in muscle from leopard frogs (Rana pipiens). The Na(+) complexed in muscle and liver was found to be 36.6 +/- 4.6% and 66.1 +/- 3.5% respectively. A temperature decrease from +34 degrees C to -2 degrees C results in a 20% decrease in the mobility of the free Na(+) in the fresh muscle. This 20% decrease in mobility results in about 50% of the free Na(+) at 34 degrees C being complexed at the lower temperature.