GEORGE T. SCOTT AND HUGH R. HAYWOOD 39 



3 seconds in isotonic sucrose; one set was blotted three times according to the 

 standard procedure while the surfaces of the other samples were brushed 

 lightly with absorbent tissue to remove grossly the adherent sucrose only from 

 the surface. In this second group, then, the extracellular space has not been 

 blotted out of the tissue. The samples were weighed, dried, extracted and 

 analyzed. Average sodium and potassium values are presented in table 2. It 

 can be seen that the lightly blotted samples actually have less sodium than the 

 triple-blotted samples. Since as shown above the triple blotting almost com- 

 pletely removes the inulin space, these data clearly indicate that the smaller 

 solutes in the extracellular space very rapidly diffuse from this space (1-3 sec. 

 here) in isotonic sucrose. Further, it can be seen that the relative difference 

 in sodium concentration between the two sets of samples is exactly equal to the 

 relative potassium difference (row d). Since the potassium concentration in sea 

 water and in the isotonic sucrose is so small relative to the total amount of 



Table 2. Potassium and sodium values for samples of ulva removed from sea water 



K Na 



a. Very light blot 21.8 13.5 



b. 'Triple-blot' 31 -o 19.2 



c. b—a 9.2 5.7 



d. c/a X 100 42.2% 42.1% 



All samples rinsed 1-2 seconds in isotonic sucrose. Some were brushed to remove sucrose 

 from surface (a), while the rest were 'triple-blotted' (b). Values are expressed as mEq/ioo gm 

 cell water. 



potassium in the cells, this difference in potassium content is probably almost 

 exclusively due to weight differences: that is, the lightly blotted samples will be 

 heavier because of the sucrose solution which was not blotted in these samples. 

 Hence there will appear to be less potassium (and sodium) per unit weight in 

 the lightly blotted samples. Since the percentage sodium difference is identical 

 with the percentage potassium difference, it is presumably to be accounted for 

 by the same explanation. Sodium and potassium ions, then, diffuse very rapidly 

 from the extracellular space of the samples after they are transferred from sea 

 water to isotonic sucrose. 



The possibility that the sucrose rinse washes out some of the electrolytes from 

 within the cell is remote, since samples removed after 30 and 60 seconds in 

 sucrose are not appreciably different in sodium and potassium content from 

 those removed after only i to 3 seconds. 



These experiments indicate that the 30-second rinse in sucrose plus the blot- 

 ting procedure remove essentially all of the extracellular sodium and potas- 

 sium and essentially none of the intracellular fractions of these cations. Hence 

 the data presented represent true cellular sodium and potassium concentrations. 



