AJP - Renal Physiology, Vol 259, Issue 5 778-F782, Copyright © 1990 by American Physiological Society
Ion concentrations in the rat CCD: differences between cell types and effect of alkalosis
J. D. Gifford, J. H. Galla, R. G. Luke and R. Rick
Department of Physiology and Biophysics, University of Alabama, Birmingham 35294.
We have previously shown that the isolated perfused cortical collecting
duct (CCD) from chloride-depleted alkalotic (CDA) rats continues to secrete
HCO3 for up to 3 h. To determine whether the sustained alteration in
transport was associated with changes in intracellular ion concentrations,
we performed energy-dispersive X-ray microanalysis in microdissected tubule
bundles obtained from CDA rats and rats with normal acid-base status (CON).
Before analysis, the bundles from both groups were incubated for 1 h in
vitro in a modified Ringer solution (pH 7.4, 105 mM Cl). Principal (PC) and
intercalated cells (IC) of the CCD from CON animals differed in the nuclear
concentration of Na (17.0 vs. 24.7 mmol/l cell water), K (192.5 vs. 177.0
mmol/l cell water), and Cl (17.8 vs. 47.8 mmol/l cell water). Cells of the
cortical thick ascending limb of Henle (CTAL) had the lowest Na and Cl
values (11.5 and 14.8 mmol/l cell water, respectively). CDA resulted in no
systematic Cl changes. In the IC the nuclear Na concentration was
significantly increased (32.0 vs. 24.7 mmol/l cell water) and in all cells
a small reduction in K concentration was detectable. These findings suggest
that 1) the different transport functions of IC, PC, and CTAL are
associated with differences in the intracellular ion composition, and 2)
the sustained HCO3 secretion seen in CCD from CDA rats cannot be explained
as the result of intracellular Cl depletion.
