THE STRUCTURAL AND FUNCTIONAL ASPECTS OF THE HANDLING OF GLUCOSE BY THE NEPHRONS AND THE KIDNEY AND THEIR CORRELATION BY MEANS OF STRUCTURAL-FUNCTIONAL EQUIVALENTS*

Abstract

A statistical study of the normal human kidney has been made by microdissection to determine the structural dimensions of the parts of the nephron (the glomeruli) through which glucose enters the tubule fluid and of the segments (the proximal convolutions) which remove it. On the basis of this analysis certain structural-functional equivalents have been proposed. When these are substituted in the theoretical functional description of the handling of glucose by the normal kidney and its constituent nephrons, it is possible to calculate such characteristics of renal activity as glomerular activity (r); total glomerular activity (R); r/R; glomerular filtration rate (GFR); maximal tubular reabsorption of glucose (TmG); and GFR/TmG. Within accepted limits of observational and statistical error, the values thus calculated from the structural data are identical with those derived from the functional measurements. It is also possible to duplicate in quantitative terms the functional titration curve which describes the over-all process of the handling of glucose by the kidney by means of these structural-functional equivalents. The splay in the titration curve of the kidney appears as a result of a certain heterogeneity in the functional activity of its constituent nephrons which correlates quantitatively with the variability of their structural dimensions.