184 



P. A. Desaulles 



hour onward it induces a clear-cut reduction in potassium 

 excretion, which reverts to normal in the ninth hour. On 

 animals of the adult group aldosterone has practically no 

 effect at all. In old rats, however, aldosterone markedly 

 enhances potassium excretion. 



f.d 



1.6 

 lA 

 1,2 

 1,0 

 Q8 

 0,6 

 OA 

 0,2 



\ Z ■} 4. ? 6 7 8 9 f 



Fig. 3. Urinary sodium/potassium ratio of adrenalectomized male 



rats of different age groups treated with aldosterone. 

 Ordinate : Difference between sodium /potassium ratio of experi- 

 mental animals and controls. 

 Other figures as for Fig. 1. 



If we consider the sodium/potassium ratio, we observe that 

 aldosterone reduces it markedly during the first hours of the 

 experiment in all groups (Fig. 3), its maximum occurring in 

 the first collecting period for young and adult groups, and 

 showing a certain delay (three hours) and greater intensity 

 ( — • 95 against —0 • 75 to —0 • 80) in the old age group. From 

 the fourth hour onward there is an increase in the ratio for 



