title: Demonstration of active potassium secretion in the late distal tubule.
abstract: 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.
mesh_terms: D000818:Animals; D001693:Biological Transport, Active; D004848:Epithelium / Q000502:physiology; D007684:Kidney Tubules / Q000502:physiology*; D007686:Kidney Tubules, Distal / Q000502:physiology*; D007700:Kinetics; D008297:Male; D008564:Membrane Potentials; D011188:Potassium / Q000378:metabolism*; D011191:Potassium Deficiency / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D011188:Potassium