226 General Discussion 



Kennedy: Morrison and Gordon (1957. Fed. Proc, 16, 366, and 

 personal communication) have reported that a 24-month-old rat 

 starved of food but not water for 24 hours loses far more urea, 

 creatinine and potassium than a young one of comparable weight. 

 So there is a state of incipient potassium deficiency. We have also 

 found that the adrenals are usually pretty large in these old rats. 



Shock: We have a done good many metabolic balance studies on 

 the human (Duncan et al. (1951). J. din. Invest., 30, 908; Duncan et 

 al, (1952). J. Geront, 7, 351 ; Bogdonoff ^/ al, (1953; 1954). J. Geront., 

 8, 272; 9, 262; Watkin et al, (1955). J. Geront, 10, 268). We consis- 

 tently found that the older individuals, when given good protein in- 

 takes that resulted in positive nitrogen balances, retained potassium 

 in excess of the theoretical amount required for the nitrogen retained. 

 A good deal of this, I am sure, may be due to cumulative analytical 

 errors, but it has always seemed to me that the older animal will 

 work himself into a potassium deficiency if given the opportunity. 



Black: Is not some of our difficulty here due to the limitations of 

 morphology? If we take as our criteria of morphological change the 

 fact that the tissue ' looks bad ' or ' looks moth-eaten ', then we are not 

 going to get anywhere in deciding the cause of this change. You can 

 hardly expect a cell to have a signpost saying ' I am too old ', or 'I 

 am potassium-deficient', and if we see the same change I do not see 

 how we can expect morphology to decide its aetiology. 



Talbot: When you use the term 'potassium-deficient', Prof. 

 Wallace, do you wish us to think simultaneously about the correlated 

 fact of the cellular sodium excess? Cellular sodium intoxication may 

 actually be the provocative factor under some circumstances. 



Wallace: Sodium excess is usually a corollary but not always. Some 

 cation, it would seem, must replace the deficit. Basic amino acids 

 have been shown to increase in potassium-deficient tissues as well as 

 sodium. 



Talbot: We have just done some experiments where the absolute 

 losses of potassium due to starvation were greater per rat than some 

 of the losses incurred when feeding a zero potassium-normal sodium 

 intake. The animals which had lost this large amount of potassium 

 by simple depletion were asymptomatic ; it was only those that also 

 had cellular sodium intoxication that showed all the symptoms com- 

 monly considered characteristic of marked potassium deficiency. 



Hingerty: Prof. Wallace, when you restored the potassium, morpho- 

 logically the tissue appeared perfectly all right in 36 hours. Did you 

 do the chemical analysis? 



Wallace: Yes, we did, stimulated by your work (Conway, E. J., 

 and Hingerty, D. J. (1948). Biochem. J., 42, 372). Unlike you we 

 found that sodium was lost simultaneously with a gain of muscle 



