The Sodium and Potassium Exchange between Intact Frogs and Their Environment

Intact living frogs (Rana pipiens) were partially immersed in dilute salt solution labeled with K⁴² or Na²⁴ or, alternatively, injected with Ringer’s fluid containing the appropriate isotope and then partially immersed in unlabeled dilute salt. Before isotopic equilibrium, the animals were sacrificed and specific activities of K⁴² and Na²⁴ were determined for medium, skin, plasma, and other tissues. With Na²⁴, entering from the medium or escaping to the medium, specific activities of the skin approach that of the plasma. For K⁴², entering from the medium, the specific activity exceeds that of the plasma. The results are interpreted as indicating that the exchange rate for Na is greater plasma to skin than medium to skin, with the reverse situation for K. Values are given for average Na, K, and Cl contents of the various organ systems.