title: The transtubular potassium concentration in patients with hypokalemia and hyperkalemia.
abstract: 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.
authors.affiliation: Renal Division, St. Michael's Hospital, University of Toronto, Canada.
authors.forename: J H
authors.initials: JH
authors.lastname: Ethier
authors.forename: K S
authors.initials: KS
authors.lastname: Kamel
authors.forename: P O
authors.initials: PO
authors.lastname: Magner
authors.forename: J
authors.initials: J
authors.lastname: Lemann
authors.forename: M L
authors.initials: ML
authors.lastname: Halperin
mesh_terms: D003900:Desoxycorticosterone / Q000494:pharmacology; D004032:Diet; D005438:Fludrocortisone / Q000494:pharmacology; D006801:Humans; D006929:Hyperaldosteronism / Q000378:metabolism; D006947:Hyperkalemia / Q000378:metabolism*; D007008:Hypokalemia / Q000378:metabolism*; D007684:Kidney Tubules / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*; D012016:Reference Values
chemical_list: D003900:Desoxycorticosterone; D011188:Potassium; D005438:Fludrocortisone