Related Experiment Videos
Receptor binding profile of Otilonium bromide
S Evangelista1, A Giachetti, B Chapelain
1Menarini Ricerche S.P.A., Firenze, Italy.
Abstract:
The interaction of Otilonium bromide (OB) with binding sites for 63 different receptors and ion channels in appropriate preparations has been investigated. Experiments were also performed in rat colon, the preferred tissue for OB 'in vivo' uptake after oral administration. Among the receptors investigated OB binds with sub microM affinity to muscarinic M1, M2, M4, M5 and PAF receptors and with microM affinity to the diltiazem binding site on L type Ca2+ channels. In the rat colon OB shows competitive interaction with the verapamil binding site on L type Ca2+ channels and with muscarinic M2 receptors with IC50 of 1020 and 1220 nM, respectively. These findings provide a molecular rationale to explain the spasmolytic action exerted by OB on intestinal smooth muscle. In particular, a combination of antimuscarinic and Ca2+ channel blocker properties seems to best account for the action of this compound.
Insights
Otilonium bromide (OB) acts as an antispasmodic by blocking muscarinic receptors and L-type calcium channels. This dual action provides a molecular basis for its effectiveness in relieving intestinal smooth muscle spasms.
Area of Science:
- Pharmacology
- Gastroenterology
- Molecular Biology
Background:
- Otilonium bromide (OB) is a known antispasmodic agent used for treating gastrointestinal disorders.
- Its precise molecular mechanisms of action, particularly its interactions with various receptors and ion channels, require detailed investigation.
Purpose of the Study:
- To investigate the interaction of Otilonium bromide (OB) with a wide range of receptor and ion channel binding sites.
- To elucidate the molecular targets responsible for OB's spasmolytic effects in intestinal smooth muscle.
Main Methods:
- Binding assays were performed to assess OB's affinity for 63 different receptors and ion channels.
- In vivo experiments were conducted using rat colon tissue to evaluate OB's interactions with specific targets.
- Inhibition constants (IC50) were determined for competitive interactions with verapamil binding sites on L-type Ca2+ channels and muscarinic M2 receptors.
Main Results:
- OB demonstrated sub-micromolar affinity for muscarinic M1, M2, M4, M5, and PAF receptors.
- OB exhibited micromolar affinity for the diltiazem binding site on L-type Ca2+ channels.
- In rat colon, OB competitively interacted with L-type Ca2+ channels (verapamil site) and muscarinic M2 receptors, with IC50 values of 1020 nM and 1220 nM, respectively.
Conclusions:
- The findings suggest a dual mechanism of action for OB, involving both antimuscarinic and calcium channel blocking properties.
- This combined pharmacological profile provides a molecular explanation for OB's spasmolytic activity on intestinal smooth muscle.