AJP - Renal Physiology, Vol 241, Issue 3 219-F223, Copyright © 1981 by American Physiological Society
Tubular handling of bicarbonate and chloride in the dog
N. L. Wong and G. A. Quamme
Bicarbonate reabsorption was assessed in the superficial proximal and
distal tubule of the hydropenic dog. Tubule fluid bicarbonate concentration
was measured by determination of total CO2 with microcalorimetry. Total CO2
declined from 21 to 14 mM along the proximal tubule, which reabsorbed 56%
of the filtered bicarbonate prior to the late proximal sampling site.
Absolute bicarbonate reabsorption was 124 pmol . min-1 . mm tubule
length-1. Concurrent water reabsorption was 34% of the glomerular
filtration rate. Tubule fluid-to-ultrafilterable chloride concentration
ratio rose to 1.10 as the tubule fluid-to-blood bicarbonate ratio fell to
0.69 at the late proximal collection site. The total CO2 in distal tubule
fluid was 6 mM, indicating that 94% of the filtered bicarbonate was
reabsorbed prior to the distal tubule. It is concluded that bicarbonate is
reabsorbed in preference to chloride in the superficial proximal tubule of
the dog, which, like that of the rat, may provide a potential driving force
for water and salt reabsorption.
