Mechanisms of relaxant action of S-petasin and S-isopetasin, sesquiterpenes of Petasites formosanus, in isolated guinea pig trachea.

Abstract

We investigated the mechanisms of action of S-petasin and S-isopetasin, from Petasites formosanus Kitamura which is used as a folk medicine for treating hypertension, tumors, and asthma in Taiwan. The tension changes of tracheal segments were isometrically recorded on a polygraph. S-Petasin and S-isopetasin non-competitively inhibited cumulative histamine-, and carbachol-induced contractions with an exception that S-isopetasin produced a parallel, rightward shift of the concentration-response curve of carbachol in a competitive manner. S-Petasin also non-competitively inhibited cumulative Ca(2+)-induced contractions in depolarized (K+, 60 mM; histamine, 100 microM; or carbachol, 10 microM) guinea-pig tracheas. S-Isopetasin did in depolarized (K+, 60 mM) trachea too. The nifedipine (10 microM)-remaining tension of carbachol (0.2 microM)-induced precontraction was further relaxed by S-petasin or S-isopetasin, suggesting that no matter whether either blocked VDCCs or not, S-petasin or S-isopetasin may have other mechanisms of relaxant action. The relaxant effect of S-petasin or S-isopetasin was unaffected by the presence of propranolol (1 microM), 2',5'-dideoxyadenosine (10 microM), methylene blue (25 microM), glibenclamide (10 microM), N omega-nitro-L-arginine (20 microM), or alpha-chymotrypsin (1 U/ml). However, S-petasin (100-300 microM), but not S-isopetasin, significantly inhibited cAMP-, but not cGMP-dependent PDE activity of the trachealis. The above results reveal that the mechanisms of relaxant action of S-petasin and S-isopetasin may be primarily due to its non-specific antispasmodic and antimuscarinic effects, respectively.

• Authors: W C Ko, C B Lei, Y L Lin, C F Chen
• Journal: Planta medica (Planta Med) Vol. 67 Issue 3 Pg. 224-9 (Apr 2001) ISSN: 0032-0943 [Print] Germany
• PMID: 11345692 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Neuromuscular Depolarizing Agents
• Sesquiterpenes
• petasin
• isopetasin
• Phosphoric Diester Hydrolases
• Calcium

Topics

• Animals
• Asteraceae (chemistry)
• Calcium (metabolism)
• Guinea Pigs
• In Vitro Techniques
• Male
• Muscle Relaxation (drug effects)
• Neuromuscular Depolarizing Agents (pharmacology)
• Phosphoric Diester Hydrolases (metabolism)
• Plants, Medicinal (chemistry)
• Sesquiterpenes (chemistry, isolation & purification, pharmacology)
• Stereoisomerism
• Trachea (drug effects, physiology)