The transtubular potassium concentration in patients with hypokalemia and hyperkalemia

Am J Kidney Dis. 1990 Apr;15(4):309-15. doi: 10.1016/s0272-6386(12)80076-x.


It is advantageous to make an independent assessment of the potassium (K) secretory process and the luminal flow rate in the renal cortex to evaluate K handling by the kidney during hypokalemia or hyperkalemia. The transtubular potassium concentration gradient (TTKG) is a semiquantitative index of the activity of the K secretory process. The purpose of this study was to define expected values for the TTKG in normal subjects with hypokalemia or following an acute K load. During hypokalemia of non-renal origin, the TTKG was 0.9 +/- 0.2; in contrast, the TTKG was significantly higher during the hypokalemia of hyperaldosteronism, 6.7 +/- 1.3. The TTKG was 11.8 +/- 3.6, 2 hours after normokalemic subjects received 0.2 mg 9 alpha-fludrocortisone (9 alpha-F). To obtain expected values during hyperkalemia, normal subjects ingested 50 mmol potassium chloride; 2 hours later, the TTKG was 13.1 +/- 3.8. Therefore, the expected value for the TTKG must be interpreted relative to the concentration of K in the plasma. Circumstances were also defined where the TTKG is low despite hyperaldosteronism, namely, during a water diuresis and pre-existing hypokalemia.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Desoxycorticosterone / pharmacology
  • Diet
  • Fludrocortisone / pharmacology
  • Humans
  • Hyperaldosteronism / metabolism
  • Hyperkalemia / metabolism*
  • Hypokalemia / metabolism*
  • Kidney Tubules / metabolism*
  • Potassium / metabolism*
  • Reference Values


  • Desoxycorticosterone
  • Potassium
  • Fludrocortisone