PO4 transport in superficial and juxtamedullary nephrons in the cat: evidence for nephron heterogeneity.

Abstract

Many micropuncture studies have demonstrated a difference between the delivery of PO4 from late superficial distal convoluted tubules and final urinary PO4 excretion. This difference could be due to PO4 transport in nephron segments beyond the late distal tubule (1) or to differing transport rates in deep nephrons (2). The latter possibility would suggest that lesser amounts of PO4 delivered from deep nephrons combined with the PO4 delivered from superficial nephrons and the algebraic sum is the final urinary PO4 content. To study the role of deep nephrons in PO4 transport with particular reference to the quantitative contribution of deep and superficial nephrons, micropuncture and A-V extraction studies were performed in the cat kidney. The cat is useful as a model for the study of nephron heterogeneity of transport since the superficial and juxtamedullary cortex are drained by discrete and accessible venous drainage systems (3).