224 ELECTROLYTES IN BIOLOGICAL SYSTEMS 



gain of Na"*" = t,^ /xEq; for concentrated saline — loss of K+ = 26 /xEq, gain of 

 Na+ = 50 ^Eq. All figures are rounded out and refer to i gm of wet skin, an- 

 alyzed 8 hours from the beginning of the experiment. A large number of estima- 

 tions of fresh, normal skin have shown that it is practically free of intracellular 

 sodium. From the above results one can say, then, that in potassium-free 

 diluted saline (equivalent to 0.4 Ringer's), for every 4 potassium ions that leave 

 the intracellular compartment, i sodium ion enters it. For potassium-free 

 saline solution of physiological concentration and for concentrated saline 

 (equivalent to 1.4 Ringer's), the ratio of number of potassium ions lost/number 

 of sodium ions gained is 4: 6, and 4:8, respectively. A rather small increase of cell 

 water by skin in diluted saline and a small loss of cell water by skin in concen- 

 trated saline was seen and is indicated in figures 11 and 12, lower part. 



In short, in the absence of potassium in the baths (extracellular fluid), intra- 

 cellular potassium, which is normally high, is diminished. At the same time, 

 intracellular sodium, which is normally low, increases. This is associated with 

 diminished active sodium transfer across the skin. 



What one is actually dealing with here may be described as an ion exchange, 

 taking place in skin, in which intracellular potassium is replaced by extracellular 

 sodium. Whereas it seems that such an exchange reaction can easily be forced 

 upon the skin, under loss of the ability to actively transfer sodium, as described 

 above, it is also quite obvious from the behavior of normal skin, in which, under 

 proper conditions, vigorous active sodium transfer occurs, that provisions are 

 made in order to prevent this ion exchange from taking place. 



MOVEMENT OF CATIONS OTHER THAN SODIUM ION IN FROG SKIN 



In previous paragraphs, we have dealt with active transport of sodium chlo- 

 ride and movement of water across skin. In the following, other ion movements 

 will be discussed briefly. It has been reported that potassium is moved from the 

 skin epithelium outwards and accumulates in the outside bath of the skin (24). 

 This also can be said for Ca"'^, H+ and Mg^ (24). Knowledge concerning the 

 behavior of these cations is rather limited. With the exception of Ca++, it may 

 be reasonably safe to state that these cations are truly accumulated at the out- 

 side. Ca++ is only apparently accumulated, since the removal of water from the 

 outside fluid compartment, associated with active NaCl uptake, quantitatively 

 accounts for the increase in Ca"*^ concentration there, at least under the cir- 

 cumstances that have been studied so far. No quantitative studies have been 

 made, as yet, of the net accumulation of H+ during active NaCl uptake. One 

 knows that the pH at the outside and inside decreases and increases, respec- 

 tively, mostly by less than one unit (24). Although complete ion balances are 

 at the present time lacking, one gains from the data at hand (table 2) the im- 

 pression that relative to sodium uptake, H+ accumulation in the outside bath is 

 small. One often finds that sodium uptake slightly exceeds chloride uptake, 



