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Thromboxane A(2)-mediated Cl(-) secretion induced by platelet-activating factor in isolated rat colon
T Suzuki1, H Sakai, N Takeguchi
1Department of Pharmaceutical Physiology, Faculty of Pharmaceutical Sciences, Toyama Medical and Pharmaceutical University, 2630 Sugitani, 930-0194, Toyama, Japan.
European Journal of Pharmacology
|September 16, 2000
Summary
Platelet-activating factor (PAF) induces chloride secretion in the rat colon via thromboxane A(2) production. Inhibitors of thromboxane A(2) synthesis and receptors blocked this effect, confirming its role in colonic fluid transport.
Area of Science:
- Gastroenterology
- Physiology
- Pharmacology
Background:
- Thromboxane A(2) is identified as a secretagogue for chloride secretion in the distal colon.
- Platelet-activating factor (PAF) is known to influence various physiological processes.
Purpose of the Study:
- To investigate whether platelet-activating factor (PAF)-induced chloride secretion in the rat colon is mediated by thromboxane A(2) production.
- To elucidate the signaling pathway of PAF in colonic epithelial cells.
Main Methods:
- Isolated rat colonic mucosae were used to measure short-circuit current (Isc).
- The effects of furosemide and NPPB on PAF-induced Isc were assessed.
- Selective thromboxane A(2) receptor antagonist (KW-3635) and thromboxane synthase inhibitor (Y-20811) were employed.
- The impact of a 5-lipoxygenase-activating protein inhibitor (MK-886) was evaluated.
- Prostaglandin E(2)-induced Isc was used as a control.
Main Results:
- PAF significantly increased Isc, indicating chloride secretion, which was blocked by furosemide and NPPB.
- KW-3635 and Y-20811 inhibited PAF-induced chloride current concentration-dependently.
- The IC(50) values for KW-3635 and Y-20811 were 2.1 microM and 0.5 microM, respectively.
- MK-886 did not affect PAF-induced chloride secretion.
- Inhibitors did not alter prostaglandin E(2)-induced Isc.
Conclusions:
- PAF-induced chloride secretion in rat colonic mucosa is primarily mediated by thromboxane A(2) release.
- Thromboxane A(2) plays a key role in regulating colonic fluid secretion stimulated by PAF.
- This finding highlights a novel signaling pathway for PAF in the gastrointestinal tract.
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