Cellular mechanisms of chlorothiazide and cellular potassium depletion on Mg2+ uptake in mouse distal convoluted tubule cells

Kidney Int. 1997 Apr;51(4):1008-17. doi: 10.1038/ki.1997.141.

Abstract

The use of the distally-acting diuretic, chlorothiazide, has been reported to have important effects on renal magnesium handling. The cellular mechanisms of chlorothiazide action on Mg2+ uptake was investigated in immortalized mouse distal convoluted tubule (MDCT) cells. Intracellular free Mg2+ concentration was determined by microfluorescence. Mg2+ transport was measured as a function of change in intracellular Mg2+ concentration with time following placement of Mg2+-depleted cells into a buffer containing 1.5 mM magnesium. The uptake rate of Mg2+ into Mg2+-depleted cells was 179 +/- 28 nM/second. Mg2+ uptake was dependent on the membrane voltage as membrane hyperpolarization enhanced uptake whereas depolarization diminished transport. Chlorothiazide increased Mg2+ uptake by 58%, from 179 +/- 28 to 283 +/- 23 nM/second. The ability of chlorothiazide to stimulate Mg2+ uptake in MDCT cells was concentration-dependent and related to the diuretic-induced hyperpolarization of the plasma membrane. These studies support the notion that acute chlorothiazide administration enhances renal magnesium conservation through its effects on Mg2+ transport within the distal convoluted tubule. Since chronic chlorothiazide administration may result in hypokalemia as well as hypomagnesemia, Mg2+ uptake was determined in potassium-depleted MDCT cells. Mg2+ uptake was diminished, 80 +/- 24 nM/second, in potassium depleted cells. Hyperpolarization of the plasma membrane with the cell permanent anion, SCN-, corrected Mg2+ uptake in potassium depleted cells suggesting that the basis for diminished uptake may, in part, be due to depolarization of the membrane voltage. In summary, acute chlorothiazide stimulates Mg2+ transport in MDCT cells. We postulate that chronic chlorothiazide use may lead to hypokalemia that in turn diminishes Mg2+ transport in the distal tubule resulting in urinary magnesium-wasting.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Cell Line
  • Chlorothiazide / pharmacology*
  • Diuretics
  • Hypokalemia / chemically induced
  • Hypokalemia / metabolism
  • Ion Transport / drug effects
  • Kidney Tubules, Distal / cytology
  • Kidney Tubules, Distal / drug effects*
  • Kidney Tubules, Distal / metabolism*
  • Kinetics
  • Magnesium / metabolism*
  • Membrane Potentials
  • Mice
  • Potassium / metabolism*
  • Sodium Chloride Symporter Inhibitors / pharmacology*

Substances

  • Diuretics
  • Sodium Chloride Symporter Inhibitors
  • Chlorothiazide
  • Magnesium
  • Potassium