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Duodenal mucosal alkaline secretion, permeability, and blood flow
O Nylander1, A Hällgren, L Holm
1Department of Physiology and Medical Biophysics, Uppsala University, Sweden.
The American Journal of Physiology
|December 1, 1993
Summary
Vasoactive intestinal polypeptide (VIP) and N-omega-nitro-L-arginine (L-NNA) stimulate duodenal alkaline secretion. Nitric oxide (NO) may inhibit this secretion, with VIP and L-NNA increasing alkaline secretion via active bicarbonate transport.
Area of Science:
- Gastroenterology
- Physiology
- Molecular Biology
Background:
- Duodenal mucosal alkaline secretion is crucial for protecting the small intestine from acidic gastric contents.
- The interplay between duodenal alkaline secretion, mucosal permeability, and blood flow is not fully understood.
- Vasoactive intestinal polypeptide (VIP) and nitric oxide (NO) are implicated in regulating gastrointestinal functions.
Purpose of the Study:
- To investigate the relationship between duodenal mucosal alkaline secretion, permeability, and blood flow in rats.
- To determine the roles of VIP and NO in modulating these duodenal functions.
Main Methods:
- Anesthetized rats underwent duodenal perfusion with saline.
- Measurements included luminal alkalinization rate (LA), mucosal permeability (51Cr-EDTA clearance), effluent volume, mean arterial blood pressure (MABP), and blood flow (laser-Doppler).
- Effects of VIP and N-omega-nitro-L-arginine (L-NNA), a nitric oxide synthase inhibitor, were assessed following systemic or intraluminal administration.
Main Results:
- VIP increased LA and fluid secretion, with higher doses correlating with increased bicarbonate concentration.
- Intravenous and intraluminal L-NNA increased LA and effluent volume, indicating stimulation of bicarbonate secretion.
- Systemic L-NNA, but not intraluminal, increased mucosal permeability and decreased blood flow. Reduced MABP decreased LA and permeability.
Conclusions:
- Nitric oxide (NO) may act as an inhibitory regulator of duodenal alkaline secretion.
- Both VIP and L-NNA stimulate duodenal alkaline secretion, likely through active bicarbonate transport mechanisms.
- VIP appears to stimulate bicarbonate and fluid secretion via distinct transport pathways. No direct causal link was found between LA, blood flow, and permeability, although MABP influences permeability.