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Ca2+-sensing receptors in intestinal epithelium
L Gama1, L M Baxendale-Cox, G E Breitwieser
1Department of Physiology, School of Medicine, Johns Hopkins University, Baltimore, Maryland 21205, USA.
The American Journal of Physiology
|November 14, 1997
Summary
Calcium-sensing receptors (CaR) are expressed in human and rat intestinal cells. These receptors activate intracellular calcium signaling pathways, impacting intestinal cell function.
Area of Science:
- Cell Biology
- Gastroenterology
- Molecular Biology
Background:
- The Ca2+-sensing receptor (CaR) plays a crucial role in calcium homeostasis.
- Its presence and function in intestinal epithelial cells remain largely unexplored.
Purpose of the Study:
- To investigate the expression and functional role of CaR in intestinal epithelial cells.
- To elucidate the signaling pathways activated by CaR in the intestine.
Main Methods:
- Reverse transcriptase-polymerase chain reaction (RT-PCR) and Northern blotting were used to detect CaR mRNA expression.
- Intracellular Ca2+ levels were measured using fura 2 fluorescence in response to CaR agonists.
- Specific inhibitors (U-73122) and pertussis toxin were employed to dissect signaling pathways.
Main Results:
- CaR expression was confirmed in human (T84, HT-29, Caco-2) and rat intestinal epithelial cells.
- CaR agonists induced a rise in intracellular Ca2+ in HT-29-18-C1 cells, dependent on thapsigargin-sensitive stores.
- The Ca2+ response was mediated by phosphatidylinositol-phospholipase C (PI-PLC) signaling and was independent of pertussis toxin-sensitive G proteins.
Conclusions:
- Intestinal epithelial cells express functional CaR.
- CaR activation triggers intracellular Ca2+ mobilization via PI-PLC signaling.
- The findings suggest CaR involvement in intestinal epithelial cell differentiation and Ca2+ transport.