210 



Scientific Proceedings (68). 



126 (1058) 



The excretion of sugars by the kidney. 



By George Peirce and Norman M. Keith. 



[From the James Buchanan Brady Urological Institute of Johns 

 Hopkins University and Hospital] 



In studying the excretion of any substance by the kidney 

 there are at first glance three separate things to be considered. 



First, the passage from the blood into the kidney cell; second, 

 the transit through the cell substance; and third, the passage 

 from the cell into the lumen of the glomerulus or tubule. It is 

 obvious that if the transfer through either cell boundary is im- 

 possible that none of the substance can be excreted, and it is 

 also obvious that if anything prevents the passage through the 

 cell substance itself that the kidney will appear impermeable. 



In considering the passage of glucose through the body of the 

 cell there are two well-known facts to be borne in mind that so 

 far as we know have not received sufficient attention in this 

 connection. The first is that the kidney uses a relatively large 

 amount of oxygen and the second is that glucose is one of the main 

 sources of energy for the body in general. It is therefore very 

 probable that the kidney normally oxidizes a certain amount of 

 glucose. Hence, even if both cell boundaries are permeable for 

 glucose not all the sugar that gets into the cell will reach the lumen 

 of the tubule. Normally only the minutest trace of sugar is 

 present in the urine, whereas if the blood sugar rises beyond a 

 certain level some will appear. Although it is true that in certain 

 cases of diabetes there may be only a very slight hyperglycemia 

 yet it is in the main true that glycosuria is dependent on a more or 

 less pronounced rise in the percentage of sugar in the blood- 

 Many hypotheses have been advanced to account for this so-called 

 threshold phenomenon and I hope you will pardon me for dis- 

 missing them with the statement that none of them are generally 

 accepted. It has seemed to us that the true explanation lies 

 along the lines indicated above. The sugar normally gains 

 entrance into the kidney cells in proportion to its concentration 



