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Water channel proteins in rat cardiac myocyte caveolae: osmolarity-dependent reversible internalization

E Page1, J Winterfield, G Goings

  • 1Departments of Medicine, University of Chicago, Chicago, Illinois 60637, USA.

The American Journal of Physiology
|June 25, 1998
PubMed

Insights

Aquaporin-1 water channels are found in rat heart cells, specifically in caveolar membranes. Their interaction with caveolin-3 is disrupted by osmotic stress, leading to aquaporin-1 internalization.

Area of Science:

  • Cardiovascular Biology
  • Cellular Physiology
  • Membrane Biology

Background:

  • Aquaporin-1 (AQP1) is a water channel protein crucial for cell hydration.
  • Caveolae are specialized membrane microdomains involved in cellular signaling and transport.
  • The presence and function of AQP1 within cardiomyocyte caveolae remain largely uncharacterized.

Purpose of the Study:

  • To investigate the localization and behavior of aquaporin-1 in cardiomyocytes.
  • To determine the relationship between aquaporin-1, caveolin-3, and caveolae under varying osmotic conditions.

Main Methods:

  • Confocal immunofluorescence microscopy was employed to visualize protein localization.
  • Primary atrial myocyte cultures, dissociated atrial and ventricular myocytes, and in situ frozen sections were utilized.
  • Cells were subjected to hypertonic stress using sucrose or NaCl solutions.

Main Results:

  • Aquaporin-1 localizes to cardiomyocyte sarcolemmal caveolar membranes and subsarcolemmal cytoplasm at physiological temperatures.
  • In situ colocalization of aquaporin-1 with caveolin-3 is reversibly disrupted by hypertonic conditions.
  • Hypertonic stress induces caveolar closure, swelling, and reversible aquaporin-1 internalization; AQP1 does not colocalize with caveolin-3 at 4°C.

Conclusions:

  • Caveolae may dynamically open and close in vivo under near-isotonic conditions.
  • Aquaporin-1 and caveolin-3 colocalization appears to be energy-dependent.
  • Closed caveolae may function as transient osmometers, responding to myocyte water flow.

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