COMPARATIVE STUDY OF MEMBRANE PERMEABILITY 625 



saline having the following composition: 113 niM NaCl; 1-9 mM KCl; 

 0-45 niM CaCU; phosphate buffer pH 7-0. RSO4 means the same saline 

 in which CI has been replaced by an equivalent amount of SO4. RSO^- 

 Na/io means sulphate saline containing ten times less Xa than the physio- 

 logical saline. RSO4-K x 10 means sulphate saline containing ten times 

 more K than the physiological saline. RSOj-Xa/io-K x 10 is a sulphate 

 saline containing ten times less Xa and ten times more K than the physio- 

 logical saline. RSO4-K 10 is a sulphate saline containing ten times less K 

 than the physiological saline. 

 It can be seen that : 



(i) The replacement of CI by SO4 is without any effect on the potential 

 difference across the small intestine, contrary to the situation in the colon 

 where the potential difference increases (expt. A). 



(2) In a sulphate saline, a decrease in Xa concentration in the mucosal 

 solution results in the inversion of the potential difference across the small 

 intestine. In the colon, we observe a decrease in potential difference 

 (expt. B). 



(3) In sulphate saline, a decrease in X*a concentration in the serosal 

 solution increases the potential difference across both small intestine and 

 colon (expt. C). 



(4) In normal saline, alterations in Xa concentrations in the mucosal 

 or serosal solutions, result in the same variations as in SO4 saline. The 

 variations are nevertheless not so important (expts. D and E). 



(5) In sulphate saline, if the concentration in K is increased in the 

 mucosal solution, the potential difference across the colon and the small 

 intestine is unaffected (expt. F). 



(6) However, it is possible to show that the K concentration in the 

 mucosal solution affects the potential difference in the intestine if we 

 decrease first the Xa concentration. The result is an inversion of the 

 potential difference. If one then increases the K concentration, the poten- 

 tial difference decreases in the small intestine while it stavs constant in the 

 colon (expt. H). 



(7) In sulphate saline, an increase in K concentration in the serosal 

 solution results in an inversion of the potential difference across the small 

 intestine and in a decrease of the potential difference in the colon (expt. G). 



(8) In sulphate saline, a decrease in Xa concentration in the serosal 

 solution increases the potential difference across the small intestine and 

 the colon. If the K concentration is increased, the potential difference 

 decreases (expt. I). 



(9) In sulphate saline, a decrease in K concentration in the mucosal or 

 in the serosal solution is without appreciable effect on the potential 

 difference across both the colon and the small intestine (exts. J. and K). 



VOL. n. 2S 



