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Regulatory volume increase after secretory volume decrease in colonic epithelial cells under muscarinic stimulation.
Ken-ichi Manabe1, Takahiro Shimizu, Shigeru Morishima
1Department of Cell Physiology, National Institute for Physiological Sciences, Myodaiji-cho, 444-8585 Okazaki, Japan.
Pflugers Archiv : European Journal of Physiology
|July 10, 2004
Summary
Colonic secretory cells shrink and then increase volume upon carbachol stimulation. This involves calcium signaling for shrinkage and the Na+-K+-2Cl- cotransporter for volume recovery in guinea-pig and human cells.
Area of Science:
- Cell Biology
- Physiology
- Gastroenterology
Background:
- Colonic epithelial cells play a crucial role in fluid and electrolyte balance.
- Understanding cellular volume regulation is key to comprehending colonic function and dysfunction.
Purpose of the Study:
- To investigate volume changes in colonic secretory cells stimulated by carbachol (CCh).
- To elucidate the underlying ionic mechanisms of CCh-induced cell volume responses.
Main Methods:
- Two-photon laser scanning microscopy to measure guinea-pig colonocyte volume.
- Electronic sizing technique for human T84 colonocyte volume.
- Intracellular calcium measurements using fura-2.
- Ionic manipulations of extracellular solutions.
Main Results:
- Carbachol (CCh) induced cell shrinkage (secretory volume decrease, SVD) followed by regulatory volume increase (RVI) in both guinea-pig and human colonocytes.
- SVD was dependent on intracellular calcium and blocked by atropine and niflumic acid.
- RVI was dependent on extracellular Na+, K+, Cl-, and the Na+-K+-2Cl- cotransporter, as shown by bumetanide sensitivity.
Conclusions:
- Colonic epithelial cells exhibit a calcium-dependent secretory volume decrease upon CCh stimulation.
- A subsequent regulatory volume increase is mediated by the Na+-K+-2Cl- cotransporter.