A Cytological Study of the Kidney Cell in Long Continued 



Hyperfunction with Relation to Hypertrophy and 



the Mitochondrial Apparatus 



Ever since the knowledge of mitochondria had passed the mere 

 descriptive stage numerous attempts have been made to interpret their 

 physiological significance. This investigation was undertaken in order to 

 determine whether wide variations in the duration and degree of experi- 

 mentally induced renal activity were associated with any demonstrable 

 peculiarities in the mitochondrial content and general cellular structure of 

 the renal tubules. Part of the tissues for this study were obtained through 

 the courtesy of Dr. Addis and Mr. Shevky of the Division of Medicine, 

 who have kindly contributed the life history of the animals used. 



NOTE BY T. ADDIS AND A. E. SHEVKY ON THE LIFE HISTORY OF 



THE MATERIAL DEALT WITH 



(From the Division of Medicine) 



There is no direct method by which the "work" of the kidney can be measured, 

 but changes in rate of work may be assumed to be indicated by changes in rate 

 of metabolism. Barcroft(l)* has shown that an increased rate of urea excretion 

 is associated with an increased consumption of oxygen by the kidney, although 

 increases in sodium chloride and water excretion are not accompanied by any 

 appreciable change in gaseous metabolism. On these grounds one would expect to 

 be able to produce renal hypertrophy in intact animals by increasing the work of 

 their kidney by constantly and over a long period giving them large amounts of 

 urea in their food. At least such a result might be expected if the assumption is 

 correct that the increase in size of the remaining kidney after unilateral nephrectomy 

 is due to the additional work it has to perform. 



Twenty-four newly-weaned white rats about a month old were divided into 

 two groups as nearly as possible alike in regard to the size, weight, and ancestry 

 of the individuals of which they were composed. Each group was kept in a separate 

 cage of the type described by Robertson (2). The diet used was one shown by 

 Osborne and Mendel (3) to be adequate for growth and maintenance. It contained 

 IS gms. of lard, 33 gms. of cornstarch, 5 gms. of agar-agar, and 43.5 gms. of 

 powdered milk. In order to facilitate the combination of these ingredients into a 

 homogeneous paste into which urea could be easily incorporated we added 50 cc. 

 of whole milk for every 100 gms. of the combined foods. Urea in substance was 

 rubbed in -a mortar into that part of the food given to the urea-fed rats, and in 

 order to obviate any possibility of error a little charcoal was added at the same 

 time. For the first two months 5.5 gms. was given with each 100 gms. of food, 

 during the third month 8 gms., for the fourth and fifth months 11 gmg., and so on 

 with successive increases until from the 13th to the 16th month, when the experi- 

 ment was terminated, 17 gms. of urea was taken in every 100 gms. of food. There 



* Figures in parenthesis refer to bibliography on pages 121 and 122. 



