AJP - Renal Physiology, Vol 260, Issue 4 498-F505, Copyright © 1991 by American Physiological Society
Axial heterogeneity of rabbit cortical collecting duct
C. L. Emmons, K. Matsuzaki, J. B. Stokes and V. L. Schuster
Division of Nephrology, University of California, Los Angeles.
The rabbit cortical collecting duct (CCD) consists of three major cell
types: principal cells transport K+, beta-intercalated cells absorb Cl-,
and alpha-intercalated cells secrete H+. We used functional and
histological methods to assess axial distribution of these cell types along
rabbit CCD. In perfused CCDs, lumen-to-bath Rb+ rate coefficient (an index
of principal cell K+ transport) was not different in tubules from outer
cortex (1 mm from renal surface) compared with those from inner cortex (2
mm from renal surface), suggesting that principal cell function is
homogeneous along the CCD. In contrast, Cl- rate coefficient (a measure of
beta-intercalated cell function) was twice as high in CCDs from outer
compared with inner cortex, suggesting heterogeneity of beta-intercalated
cells along the CCD. To further investigate these regional differences, we
fixed and embedded kidneys and identified three cell types in CCD cross
sections using carbonic anhydrase staining and peanut lectin binding.
Comparing tubule cross sections from outer with those from inner cortex, we
found no axial difference in the fraction of cells that were either
principal cells (64%) or total (lectin binding and nonlectin binding)
intercalated cells (36%). However, the lectin-binding intercalated cell
subset was significantly increased in outer compared with inner cortex. We
conclude that there is not heterogeneity of principal cells along the
rabbit CCD; however, beta-cell number and function are increased in outer
CCD. Collecting duct heterogeneity begins within the cortical segment.
