Comparative Study of Membrane Permeability 



E. SCHOFFENIELS* 



Institiit Leon Fredeiicq, Laboiatoires de Biochimie, 

 I'niversite de Liege, Belgium 



The ultimate purpose of studies on the permeabihty of Hving mem- 

 branes is to obtain information concerning the organization and the 

 chemistry of such membranes. It is a well-known fact that cellular mem- 

 branes actively transport not only inorganic ions but also small organic 

 molecules. In fact the number of functions attributed to cellular mem- 

 branes is increasing rapidly with the constant progress in that field. One 

 wonders therefore how these various mechanisms are organized at the cell 

 surface. 



Thus I should like to discuss what could be called the functional 

 structure of a living membrane, i.e. the way some of the functions so far 

 identified are organized and distributed at the cell boundary. As I will 

 show later, it is possible to identify a living membrane, knowing its 

 permeability properties in exactly the same way as a svstematician identifies 

 a species using morphological features. This is the reason why I suggest 

 defining what we could call the permeability characters of a living mem- 

 brane. As far as inorganic ions are concerned, the active transport of Na, 

 CI, etc., for instance, are permeability characters. It is the same for the 

 properties of passive permeability to Na, K, CI and so on. 



The comparative study of membrane permeability ofiers many interest- 

 ing aspects since it may help us to establish not only the distribution of the 

 permeability characters in the animal kingdom but also their organization 

 within the cell membrane. Last but not least, having established the 

 functional organization of a living membrane one still has to define the 

 chemical nature of the molecular architectures responsible for the various 

 permeability characters. 



I should like to illustrate these various points by discussing some of the 

 recent work we have been doing. Miss INI. Baillien and I, in Professor 

 Florkin's laboratory. 



Let us first examine the results of potential difi'erence measurements 

 performed at various levels of the digestive tract in some animal species. 



* Chercheur qualifie du Fonds National de la Recherche Scientitique. 



