192 P. A. Desaulles 



On the sodium/potassium ratio, the efPects are comparable 

 to those obtained in males but are of greater intensity (more 

 than twice the values observed in males) and of more rapid 

 onset, and also tend to diminish rapidly with increasing age 

 (Fig. 12). 



Discussion 



From the experimental results presented, it follows that age 

 modifies the sensitivity of adrenalectomized rats to the 

 influence of the adrenal steroids investigated. These modifica- 

 tions are qualitative as well as quantitative, the sex of the 

 animals also playing an important role. 



Whereas in male rats increasing age tends to reduce to 

 control values the inhibiting effects of aldosterone on urinary 

 output, it tends in females to induce a marked secondary 

 diuretic response. The primary retention of sodium produced 

 by aldosterone is of about the same order of magnitude in all 

 animals, whether male or female, but ageing greatly increases 

 the concomitant loss of potassium, this effect being particul- 

 arly clear in male and female rats of the old age group. 



In contrast, Cortisol has an enhancing effect on diuresis 

 which, especially in females, tends to increase with advancing 

 age, whereas in males it is more intense from the onset and 

 remains of about the same order. The effects of Cortisol on 

 sodium excretion are profoundly different with advancing age 

 in rats of different sexes. In males these effects tend to dis- 

 appear completely. In females, on the other hand, they 

 appear earlier and remain of the same order of magnitude. 



After Cortisol treatment we can observe comparable dif- 

 ferences in potassium excretion. Whereas young males 

 respond with an intense potassium excretion which drops 

 rapidly as the animals grow older, these changes are only 

 moderate in females, potassium excretion remaining high 

 until old age and its onset merely retarded. 



These age and sex-bound differences become particularly 

 clear if we study the variations in the sodium/potassium ratio. 

 The sensitivity of the animals to the effects of aldosterone 



