Glandular Secretion of Electrolytes 



65 



Thorn and Schwartz, 1954; Thaysen, 1955; Schwartz and 

 Thaysen, 1956; Bulmer and Forwell, 1956; Bro-Rasmussen, 

 Killmann and Thaysen, 1956). Like sodium, potassium is 

 transferred into the precursor at a constant concentration, 

 but it is not reabsorbed in any of the glands. The rise in 

 potassium concentration at the low secretory rates in parotid 

 saliva (and in sweat?) may be secondary to reabsorption of 

 water from the precursor as indicated by Langstroth, McRae 

 and Stavraky (1938) and by Thaysen, Thorn and Schwartz 

 (1954), and/or to an exchange between sodium and potassium 

 ions during the process of sodium reabsorption. 



Table I 



Comparison between the calculated concentrations of sodium and 



POTASSIUM in the PRECURSOR SECRETIONS OF FOUR SECRETORY PRODUCTS 

 AND THE CONCENTRATIONS OF THE SAME IONS IN PLASMA WATER 



Fig. 2 shows a linear regression of the rate of sodium 

 excretion in parotid saliva on the rate of secretion. According 

 to the above hypothesis the values for slope and intercept in 

 Fig. 2 can be interpreted to mean that sodium is transferred 

 into the precursor solution at the rate of 0-112 microequiva- 

 lents per mg. of saliva discharged and that 2 • 4 microequiva- 

 lents are subsequently reabsorbed per gram gland per minute. 

 The sodium concentration of the sweat precursor has been 

 calculated in a similar manner from the data of Schwartz and 

 Thaysen (1956) and the values are compared to those of the 

 other secretions and to plasma water in Table I. According 

 to Table I the sums of the concentrations of sodium and 

 potassium in the presecretions of saliva and sweat are lower 

 than the sums of the concentrations of the same ions in the 

 two other secretions and in plasma water. No other cations 



AQEIXG — IV— 3 



