Effect of Adrenal Steroids on Body Electrolytes 193 



increases with advancing age, females showing much greater 

 differences than males. By way of contrast, sensitivity of the 

 animals to Cortisol diminishes with advancing age, females 

 showing here too a greater sensitivity than males. 



The similarity of the curves of the sodium/potassium ratio 

 for aldosterone and Cortisol is also striking and leads us to the 

 problem of (a) the primary and (b) the secondary effects of 

 these substances, and furthermore to the problem of the 

 classification of adrenal steroids on the basis of what has been 

 considered their most important physiological effects. 



From previous experiments with aldosterone one is inclined 

 to consider as primary effects both sodium retention as a 

 consequence of increased tubular resorption of sodium ion, 

 and potassium excretion as a consequence of the exchange 

 between sodium ions in the tubule cells (Cole, 1957; Stanbury, 

 Gowenlock and Mahler, 1958). Sodium retention remains of 

 about the same order of intensity and duration from youth to 

 old age in both males and females. It is concomitant potas- 

 sium excretion that rises strikingly with advancing age both 

 in males and females. 



On the other hand, the diuresis induced by aldosterone, 

 which is most apparent in old female animals in the later 

 phases of the experiment, is most probably of secondary 

 origin, its causes lying in the effect of aldosterone on the 

 sensitivity of adrenalectomized animals to endogenous anti- 

 diuretic hormone (Gaunt, Lloyd and Chart, 1956). 



As for Cortisol, its essential effect seems to lie in the very 

 marked potassium excretion which is regarded as running in 

 parallel with its catabolic effects. 



Its effect on potassium excretion tends to diminish with 

 advancing age, male animals being here more susceptible than 

 females. Conversely, the diuretic and sodium-excreting pro- 

 perties of Cortisol seem to be caused essentially by the potent 

 antagonistic effect of this steroid on the sensitivity of the 

 animal to antidiuretic hormone; these properties tend to dis- 

 appear with increasing age in males but not in females. 

 Aldosterone and Cortisol tend to induce a greater diuretic 



AGEING — IV — 7 



