AJP - Renal Physiology, Vol 245, Issue 1 83-F88, Copyright © 1983 by American Physiological Society
Demonstration of active potassium secretion in the late distal tubule
S. M. Jones and J. P. Hayslett
Studies were performed in the rat, under steady-state conditions, to
determine the mode of potassium transport in the late distal tubule. In
these experiments the potential difference and potassium activity were
measured simultaneously in steady-state fluid droplets in control rats,
during acute infusion of KCl, and in potassium-deficient rats. The results
demonstrate active potassium secretion in the late distal tubule of the
control and KCl-infused animals, since the observed potassium activity of
11.14 +/- 1.39 in control animals and 25.26 +/- 2.96 meq/liter in
potassium-loaded animals was significantly greater than the predicted
values of 7.75 +/- 0.59 and 14.01 +/- 0.94 meq/liter in the same groups,
respectively. In potassium-deficient animals, however, the observed
potassium activity in luminal fluid of 4.03 +/- 0.55 meq/liter was not
different from the predicted value of 4.26 +/- 0.32. In summary, this study
demonstrates that potassium secretion in the late distal tubule of the rat
occurs by an active process and fails to demonstrate active absorption in
the same tubular segment.
