The kidney continues to mature postnatally, with significant elongation of nephron tubules and collecting ducts to maintain fluid/electrolyte homeostasis. The aim of this project was to develop methodology to estimate lengths of specific segments of nephron tubules and collecting ducts in the CD-1 mouse kidney using a combination of immunohistochemistry and design-based stereology (vertical uniform random sections with cycloid arc test system). Lengths of tubules were determined at postnatal day 21 (P21), 2 and 12 months of age and also in mice fed a high salt diet throughout adulthood. Immunohistochemistry was performed to identify individual tubule segments (aquaporin-1: proximal tubules [PT] and thin descending limbs of Henle [TDLH]; uromodulin: distal tubules [DT]; aquaporin-2: collecting ducts [CD]). All tubular segments increased significantly in length between P21 and 2 months of age (PT: 602% increase, DT: 200% increase, TDLH: 35% increase, CD: 53% increase). However, between 2 and 12 months, a significant increase in length was only observed for PT (76% increase in length). At 12 months of age, kidneys of mice on a high salt diet demonstrated a 27% greater length of the TDLH but no significant change in length was detected for PT, DT and CD compared with the normal-salt group. Our study demonstrates an efficient method of estimating lengths of specific segments of the renal tubular system. This technique can be applied to examine structure of the renal tubules in combination with the number of glomeruli in the kidney in models of altered renal phenotype.
- proximal tubules
- distal tubules
- loop of Henle
- collecting ducts
- Copyright © 2016, American Journal of Physiology-Renal Physiology