POTASSIUM INTERCHANGE IN THE HUMAN BODY 555 



mination of the weight of the muscles from the daily creatinine excretion 

 it is assumed that the creatinine excreted has been formed in the body 

 from creatine and the daily conversion of creatine to creatinine amounts 

 to about 1.32 per cent of the weight of the creatine. From these figures 

 the creatine content of the body can be estimated to be 99 gm. Assuming 

 the creatine of the body to be located in the muscles and the creatine 

 content of the muscles to amount to 0.39 per cent of the weight of the 

 muscles, we arrive at the result that the weight of the muscles amounts 

 to 25 kgm and that, correspondingly, the muscles contain about 82 gm 

 potassium. 



About % of the potassium content of the mammalian body is found 

 in the muscles. Assuming this to be the case in the human body, we 

 arrive at the estimate that the body of the human subject in question 

 contains 110 gm potassium of which 106 gm are located in the cells. 

 The amount of extracellular potassium of the body is thus 3.6 per cent 

 of the total potassium content of the organism. In the case of total 

 interchange between extracellular and cellular potassium, only 3.6 per 

 cent of the amount of labelled potassium absorbed into the circulation 

 minus the ^^K excreted<i> should be present in the extracellular space. 

 In the case of total interchange, 1 mgm urine potassium should thus, after 

 the lapse of 48 hours, contain only 0.0010 per cent of the labelled potas- 

 sium administered. 



RESULTS 



In the first experiment, the results of which are seen in Table 1, urine 

 was collected during the first 2 days after drinking the solution containing 

 the labelled potassium chloride. The presence of easily demonstrable 

 amounts of ^^K could be shown as early as 12 minutes after drinking 

 the active solution, while a negative result was obtained after the lapse 

 of 5 minutes. The total urine was found to contain 10.5 per cent of the 

 *2K administered, the potassium content amounting to 3.4 gm. Thus, 

 1 mgm average potassium present in the urine contained 0.003 per cent 

 of the ^^K administered. This is much less than the amount which was to 

 be expected (0.012) assuming an absence of interaction between cellular 

 and extracellular potassium (see p. 554). 



The results of this preliminary experiment thus lead to the conclusion 

 that a very substantial part of the 42K absorbed into the circulation, must 

 have found its way into the tissue cells while a substantially equal number 



^1^ We found the excretion of ^^K through the bowels to make out roughly 15 

 per cent of the amount excreted through the kidneys, the total excretion of ''-K 

 in the course of the experiment being about 11 + 0.15x11 13 — per cent. 



