Insulin and IGF-I inhibit calcium-dependent chloride secretion by T84 human colonic epithelial cells

Area of Science:

• Cell Biology
• Gastroenterology
• Endocrinology

Background:

• Calcium-dependent chloride secretion is regulated by intracellular signaling pathways.
• D-myo-inositol (3,4,5,6) tetrakisphosphate [Ins(3,4,5,6)P(4)] and phosphatidylinositol 3-kinase (PI 3-kinase) activity inhibit this secretion.
• Distinguishing between these pathways is crucial for understanding cellular regulation.

Purpose of the Study:

• To investigate whether insulin, acting through PI 3-kinase, inhibits chloride secretion.
• To differentiate the roles of PI 3-kinase and Ins(3,4,5,6)P(4) in regulating colonic epithelial cell secretion.
• To explore the physiological and pathophysiological implications of insulin and IGF-I signaling in chloride secretion.

Main Methods:

• Utilized T84 colonic epithelial cell monolayers in Ussing chambers to measure chloride secretion.
• Assessed PI 3-kinase activation using Western blotting techniques.
• Investigated the effects of insulin, IGF-I, and PI 3-kinase inhibitors (wortmannin, LY-294002).

Main Results:

• Basolateral insulin and IGF-I inhibited carbachol- and thapsigargin-induced chloride secretion.
• Insulin and IGF-I did not affect Ins(3,4,5,6)P(4) levels.
• Inhibitory effects of insulin and IGF-I were reversed by PI 3-kinase inhibitors and involved recruitment of PI 3-kinase subunits.

Conclusions:

• Insulin and IGF-I inhibit calcium-dependent chloride secretion in T84 cells via a PI 3-kinase-dependent mechanism.
• This PI 3-kinase pathway is independent of Ins(3,4,5,6)P(4).
• These findings have potential physiological and pathophysiological significance given insulin and IGF-I release patterns.