Sodium and Potassium Regulation in Ulva 

 Lactuca and Valonia Macrophysa' ^ ^ 



GEORGE T. SCOTT AND HUGH R. HAYWOOD^ 



Oberlm College, Oberlin, Ohio, The Marine Biological Laboratory, The Bermuda Biological Station, 

 and the Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 



A MAJOR PROBLEM of all living systems is the maintenance within the cell 

 of a chemical composition which dififers both quantitatively and qualita- 

 tively from that of the external environment. Such regularity of cellular com- 

 position is essential to life. The maintenance of a high intracellular potassium 

 ion concentration and low sodium ion concentration, contrasted with a bathing 

 medium high in sodium and low in potassium, such as blood and sea water, is 

 a basic characteristic of cells living in these environments. This uneven distribu- 

 tion of sodium and potassium between living cells and their environments has 

 long attracted the interest of a large number of physiologists. 



Of paramount signilicance in stimulating interest in this field is the work of 

 Dr. W. J. V. Osterhout and his co-workers, who were foremost in an attempt to 

 understand the potassium-accumulating mechanism. One form which early 

 attracted the attention of Dr. Osterhout was the large coenocytic alga Valonia 

 macrophysa. As a result of investigations on this interesting organism Dr. 

 Osterhout suggested one of the first theories of potassium accumulation, 

 namely, that potassium was accumulated owing to the activity product (K) 

 (OH) being greater outside than inside because of the pn difference between 

 sap and sea water (28, 29). 



More recently evidence obtained on erythrocytes (12) and muscle (43) has 

 been interpreted in terms of a primary sodium secretion of the cell and second- 

 arily of an absorption of potassium within the cell as electro-chemical neutrality 

 is maintained. Such a theory presupposes an active transport of sodium out of 

 the cell and a passive accumulation of potassium within. A third view-point 

 has been proposed by Ling (22) who maintains that the distribution of sodium 

 and potassium between muscle cells and plasma is to be accounted for on the 



^Contribution No. 217 of the Bermuda Biological Station. 



-Contribution No. 597 of the Woods Hole Oceanographic Institution. 



^ This research was conducted under Contract No. AT(ii-i)-i8i between the U. S. Atomic 

 Energy Commission and Oberlin College. 



* Present address: University of Rochester, School of Medicine and Dentistry, Rochester, 

 N. Y. 



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