226 



ELECTROLYTES IN BIOLOGICAL SYSTEMS 



has now arisen comes from the fact that skin potentials do not drop under all 

 conditions of low extracellular potassium. Relatively high skin potentials associ- 

 ated with inside and outside leakage were observed when diluted saline (corre- 

 sponding to 0.4 Ringer's) was used (29). Very low potentials, on the other hand, 



12 



10 



4 - 



2 - 



- X CONTROL FROGS 

 • ACTH FROGS 



-I— 

 20 



MILLIVOLTS 



Fig. 13. Dependence of K""" rejection from the epithelium on skin potential. Skins of 

 normal frogs and frogs pretreated with a purified ACTH preparation. Rana pipiens. Calcium- 

 free Ringer's on both sides of the skin. For treatment of frogs 3 to 5 mg of the hormone was 

 implanted in the dorsal lymph sac and kept there for 3 days, after which the animals were 

 killed (28). 



were seen in potassium-deficient solutions of physiological or higher than 

 physiological sodium chloride levels. It is hard to understand why, then, if po- 

 tassium should be solely subjected to electrostatic forces, some of the potassium 

 should be released from the outside and another portion from the inside of the 

 skin, especially since, under conditions leading to very low skin potentials 

 (3-5 mv), the same kind of inside and outside leakage could be observed. 



