Hormones and Homeostatic Mechanisms 



171 



33-day-old rats. Thus vasopressin has a different effect in 

 23-day-old than in 33-day-old animals. Evidently there is a 



23 days 



Renal 

 water 

 loss 



Renal 



sodium 



loss 



ju^Eq/lOO g 

 450 



Renal 



potassium 



loss 



^Eq/100 g 

 450 

 300 

 •150 



. C 



I i controls 



cortisone 0.5 



cortisone 0.125 



cortisone 0.25 



Fig. 2. The effect of cortisone administered for six days in different doses on 

 renal loss of water, sodium and potassium during the first three hours after 

 administration of a water load (4-5 ml./lOO g. body wt.) to young rats aged 



23 and 33 days. 



change in the reactivity of the kidneys to this hormone at 

 that period. This might be due to functional differences in 



