Journal of Applied Physiology, Vol 40, Issue 6 1009-1011, Copyright © 1976 by American Physiological Society
Comparison of proximal tubule fluid-to-plasma ultrafiltrate chloride ratio in rats and dogs
G. R. Marchand, C. E. Ott, J. L. Cuche and F. G. Knox
Previous studies in rats have demonstrated that the concentration of
chloride in proximal tubule fluid is greater than that in plasma. The
gradient reaches a free-flow steady-state level in the early proximal
tubule and is maintained throughout the accessible proximal tubule. On the
other hand, studies in dogs are in conflict regarding either the existence
of a gradient or the development of a free-flow steady-state level. Since a
species difference of tubule fluid to plasma chloride (TF/PC1) may exist,
the present study was done to systematically compare the tubule fluid to
ultrafiltrate chloride ratio (TF/UFC1) in hydropenic rats and dogs during
normal acid-base balance. Chloride was analyzed by microelectrometric
titration. In the rat the TFC1 and UFC1 concentrations were 139 +/- 1.4 and
120 +/- 1.2 meq/1, respectively. In the dog the TFC1 and UFC1
concentrations were 138 +/- 1.3 and 121 +/- 1.5 meq/1, respectively. Thus,
there was no significant difference in the TF/UFC1 ratio between the rat
(1.17 +/- 0.02) and the dog (1.14 +/- 0.01). Furthermore, regression
analysis indicates that there is no correlation between TF/UFC1 and TF/PIn
in either the rat or dog, which suggests that the gradient originates early
in the proximal tubule and is maintained throughout the accessible proximal
tubule in both species.
