What is responsible for the diurnal variation in potassium excretion?

Am J Physiol. 1994 Aug;267(2 Pt 2):R554-60. doi: 10.1152/ajpregu.1994.267.2.R554.


Potassium excretion exhibits a diurnal pattern, with most excretion occurring close to noon in humans. Each component of the K+ excretion rate [urinary K+ concentration ([K+]) and flow rate] was measured and back-calculated to reflect events in the cortical collecting duct (CCD). Our purpose was to determine to what extent each component contributed to this diurnal variation in each 2-h portion of the day. In humans, K+ excretion rose threefold from nadir (0600 h) to peak (1200-1400 h), 18 h after the principal intake of K+. The variation in K+ excretion was due almost exclusively to changes in [K+] in the terminal CCD ([K+]CCD) rather than via changes in flow rate. In rats, the bulk of K+ excretion occurred shortly after eating. Both components of K+ excretion rose after meals; the rise in the [K+]CCD (3.3-fold) predominated at earlier times, and the rise in flow rate occurred later and was primarily a result of a higher rate of excretion of urea. The rise in [K+]CCD did not correlate with aldosterone levels or administration. A very large rise in the [K+]CCD only occurred in the presence of bicarbonaturia; the transtubular potassium concentration gradient was now close to 15 in the morning and evening.

MeSH terms

  • Acetazolamide / pharmacology
  • Adult
  • Animals
  • Bicarbonates / urine
  • Circadian Rhythm*
  • Female
  • Humans
  • Kidney Tubules / metabolism
  • Kidney Tubules, Collecting / metabolism
  • Male
  • Mineralocorticoids / pharmacology
  • Osmolar Concentration
  • Potassium / metabolism
  • Potassium / urine*
  • Rats


  • Bicarbonates
  • Mineralocorticoids
  • Acetazolamide
  • Potassium