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Published on: September 18, 2013
Epidermal growth factor up-regulates intestinal Na+/H+ exchange activity
F K Ghishan1, K Kikuchi, B Riedel
1Department of Pediatric Gastroenterology, Vanderbilt Medical Center, Nashville, Tennessee 37232.
Summary
Epidermal growth factor (EGF) stimulates sodium-hydrogen exchange (Na+/H+) activity in rat jejunal enterocytes by increasing the Vmax. This effect is ATP-dependent and does not involve the phosphatidylinositol pathway.
Area of Science:
- Cell Biology
- Physiology
- Biochemistry
Background:
- Sodium-hydrogen exchange (Na+/H+) is crucial for cellular homeostasis.
- Epidermal growth factor (EGF) is a key regulator of cellular processes.
- Understanding EGF's role in intestinal epithelial transport is vital.
Purpose of the Study:
- To investigate the regulation of Na+/H+ exchange activity by EGF in rat jejunal enterocytes.
- To determine the kinetic parameters (Vmax and Km) of Na+/H+ exchange under EGF stimulation.
- To explore the involvement of second messengers and ATP in EGF-mediated Na+/H+ regulation.
Main Methods:
- Isolation of brush-border membranes from rat jejunal enterocytes.
- Measurement of Na+/H+ exchange activity using in vitro assays.
- Incubation with EGF, second messengers (phorbol esters, calmodulin, cyclic AMP), and ATP depletion.
- Kinetic analysis of Na+/H+ exchanger activity (Vmax and Km).
Main Results:
- EGF significantly stimulated Na+/H+ exchange activity in a concentration-dependent manner.
- The stimulation by EGF was attributed to an increase in Vmax, not Km.
- EGF, calmodulin, cyclic AMP, and phorbol ester effects were ATP-dependent.
- EGF stimulation was not mediated by the phosphatidylinositol pathway.
Conclusions:
- EGF enhances Na+/H+ exchange activity in jejunal enterocytes.
- The mechanism involves an ATP-dependent increase in the transporter's maximal velocity (Vmax).
- EGF's regulatory pathway for Na+/H+ exchange likely bypasses phosphatidylinositol signaling.
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