Regulatory phosphorylation of the secretory Na-K-Cl cotransporter: modulation by cytoplasmic Cl

Am J Physiol. 1996 Feb;270(2 Pt 1):C437-48. doi: 10.1152/ajpcell.1996.270.2.C437.


The effect of cytoplasmic Cl concentration ([Cl]i) on the activation state ([3H]benzmetanide binding rate) and phosphorylation state (32P incorporation) of the Na-K-Cl cotransporter was evaluated in secretory tubules isolated from the dogfish shark rectal gland. Reduction of [Cl]i at relatively constant cell volume (by removal of extracellular Cl or Na or by addition of bumetanide) increased cotransporter activation and phosphorylation. Raising extracellular K concentration ([K]o) from 4 to 80 mM, a maneuver that elevated [Cl]i above normal, reduced basal cotransport activity and rendered it entirely refractory to forskolin. High [K]o also blocked activation and phosphorylation in response to cell shrinkage, despite the fact that [Cl]i was already greatly elevated as a consequence of osmotic water loss. The phosphatase inhibitor calyculin A also promoted activation, but not in cells preexposed briefly to high [K]o. In summary, maneuvers than lower [Cl]i activate the cotransporter, whereas those that elevate [Cl]i (or prevent it from decreasing) block activation in response to secretory stimuli. Cell Cl appears to govern its own rate of entry via Na-K-Cl cotransport by impeding regulatory phosphorylation of the Na-K-Cl cotransport protein.

Publication types

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

MeSH terms

  • Animals
  • Carrier Proteins / metabolism*
  • Chlorides / metabolism*
  • Cyclic AMP / pharmacology
  • Cytoplasm / metabolism*
  • Ions
  • Marine Toxins
  • Osmolar Concentration
  • Oxazoles / pharmacology
  • Phosphoric Monoester Hydrolases / antagonists & inhibitors
  • Phosphorylation
  • Potassium / pharmacology
  • Salt Gland / cytology
  • Salt Gland / metabolism
  • Sharks
  • Sodium-Potassium-Chloride Symporters
  • Time Factors


  • Carrier Proteins
  • Chlorides
  • Ions
  • Marine Toxins
  • Oxazoles
  • Sodium-Potassium-Chloride Symporters
  • calyculin A
  • Cyclic AMP
  • Phosphoric Monoester Hydrolases
  • Potassium