Intrarenal heterogeneity. The case for two functionally dissimilar populations of nephrons in the mammalian kidney

In the past few years evidence has established that the rat kidney has at least two functionally dissimilar groups of nephrons, corresponding to known anatomic differences: the superficial nephron, comprising the bulk of nephrons in most species; and the juxtamedullary nephron, constituting the remainder. The filtration rate, the composition of tubule fluid in Henle's loop, the response to acute and chronic salt loads, and the effect of chronic hypertension have been shown to differ between the two kinds of nephrons. It may be useful to bear in mind the concept of two nephron populations in the study of renal disease, since certain diseases have been observed by morphologists to have a predilection for specific anatomic regions within the kidney. Interpreting function with an eye to underlying structure may prove as rewarding today as it was to William Bowman 131 years ago.