Ion Transtort and Ion Exchange in Frog Skin 



ERNST G. HUF 



Department of Physiology^ Medical College of Virginia, 

 Richmond, Virginia 



NOT SO LONG AGO, Gcorgc Wald (77) said that, "Probably the most 

 significant development in modern biology is that it had begun to 

 meet its classic problems on the molecular level." I feel that many or perhaps 

 most of the physiologists would subscribe to this, with respect to their problems. 

 There is a strong trend towards 'Molecular Biology' (32). In pursuing such a 

 course, one inevitably becomes involved in the fundamental mechanisms of 

 uptake and transport of molecules and of ions. It is quite significant to notice 

 that those interested in unraveling the functions of the kidney also find it 

 necessary, or at least helpful, to study papers dealing with such subject matter 

 as the penetration of substances into a single cell — such as a Valonia cell; the 

 electrolyte equilibria in muscle and nerve; and the uptake of ions by frog 

 skin or the gills of a fish, to mention only a few examples. At the molecular 

 level, there is a great similarity of mechanisms which allow the penetration of 

 certain molecules and ions or which provide for active transport of certain 

 uncharged or charged particles from a lower to a higher electro-chemical poten- 

 tial, in which case expenditure of energy by the cell is required. In trying to 

 understand the function of organs, physiologists are becoming increasingly 

 aware of the importance of the fine structure of tissues, the cell surface and 

 also of ultra structures and surfaces within cells of which all organs are com- 

 posed. The aim in 'molecular biology' is to interpret cell functions as physico- 

 chemical reactions between free molecules or ions and fixed structural elements 

 of the living cell. For this, the analytical as well as creative minds of Osterhout 

 and Jacobs have helped, to a considerable extent, to lay the ground work. 



This presentation is based on a selected group of papers on active ion trans- 

 port, and although a fairly large number of them are included here, others 

 had to be excluded at this time. For more complete information, several reviews 

 of the subject in question are available (23, 72, 74, 75, 76). One of the most 

 revealing of recent papers is that by Linderholm (45), who is working in 

 Teorell's laboratory. 



The field of permeability and transport of water and salt across cell and 

 tissue membranes was called to my attention by Dr. Albrecht Bethe who, 

 during the earlier years of my scientific endeavors, was working on osmo- 



