Discussion 18 



the response of older animals with that of adults: they became com- 

 parable in quantitative terms only when the rats were 17-22 days old. 



There is another point on which I should like to have your view s, Prof. 

 Adolph. We find that these responses of infant rats to vasopressin are 

 influenced not only by the age of the animals, but also by the litter size. 

 In other words, if there are fewer animals in the litter, they will be larger, 

 and that may influence the development of renal functions. 



Adolph : We have not tested for litter size. In general we have used the 

 larger animals. 



Black: I must apologize for introducing another hormone, but Prof. 

 Adolph's interesting observation reminded me of some recent work on 

 hypertonic over-hydration by INIcCance and Widdowson (1957. Acta 

 Paediat., (Uppsala), 46, 337). W^e may be tacitly assuming that in these 

 poor responses we are dealing with either renal immaturity or with this 

 very interesting hypotension, and I wondered whether the adrenal gland 

 came into this at all, since its histology changes very considerably from 

 foetal to neonatal life. Could a better water diuresis be obtained in these 

 newborn animals by giving them cortisone with the water load? 



Adolph: Dr. Falk did some work on the administration of the cortical 

 adrenal substances. At the early ages these seem to have very little 

 effect on water diuresis and water excretion. 



Swyer : I cannot speak about the rat, but so far as the human is con- 

 cerned the evidence seems to be that the infant adrenal is quite effective 

 in secreting glucocorticoids and probably aldosterone, at least in amounts 

 relative to its own size, so that the apparently deficient response of the 

 kidney does not appear to be due to lack of adrenal steroids. You cannot 

 improve the renal response by giving steroids. It might be a lack of renal 

 responsiveness to the water load rather than any insufficiency of hor- 

 monal equipment. 



Heller: We have found (Heller, H. (1958). Mschr. Kinderheilk., 106, 

 81) that injections of cortisone into newborn or infant rats produce a 

 significant decrease of total bodv water. Much the same effect is obtained 

 with ACTH. 



Adolph : I should like to make a small protest against the use of the 

 term 'renal immaturity'. If you want the 100-day-old rat to be the 

 criterion of everything, then everything else is either premature or 

 postmature. But if you want to consider that every animal has an opti- 

 mum for its own age, then the use of the word immaturity seems to me 

 undesirable. The same thing applies to hypotension: what is hypo- 

 tension for an adult is not hypotension for an infant. 



Talbot: I should like to register a mild objection to this thesis about 

 immaturity. For instance one might say that the parathyroid-renal 

 phosphorus homeostatic mechanism of the human infant is at least 

 functionally immature at birth, presumably because the mother's 

 mechanisms have performed this homeostatic task for the infant while 

 it was in utero. As a result, the infant has a very small tolerance for 

 dietary phosphorus at birth. However, he develops the capacity to 

 handle phosphorus satisfactorily within a few weeks. 



Have you any further information about this adrenaline-induced 



