title: Mechanism involved in the spasmolytic effect of a mixture of two triterpenes, cycloartenol and cycloeucalenol, isolated from Herissanthia tiubae in the guinea-pig ileum.
abstract: The smooth muscle relaxant properties of a mixture of the two triterpenoids cycloeuclalenol and cycloartenol (CC) isolated from Herissanthia tiubae (Malvaceae) were studied in several smooth muscle preparations. CC inhibited contractions induced by carbachol, histamine and KCl in the guinea-pig ileum, but no spasmolytic activity was found in guinea-pig trachea or rat aorta. In guinea-pig ileum, concentration-response curves to carbachol and CaCl (2) in high K(+) were shifted to the right by CC in a concentration-dependent manner with slopes of the Schild plot differing from the unity. IC(50) values were 3.4 +/- 0.8 x 10 (-5) M and 8.44 +/- 1.87 x 10 (-5) M for carbachol and CaCl(2), respectively. The phorbol ester TPA, which activates protein kinase C (PKC), potentiated contractions induced by submaximal concentrations of carbachol. This potentiation was inhibited by CC. Desensitization of PKC by TPA completely abolished the inhibition produced by CC on carbachol-induced contractions. Together, our results indicate that inhibition of PKC is involved in the spasmolytic effect of CC in the guinea-pig ileum.
authors.affiliation: Laboratório de Tecnologia Farmacêutica, Universidade Federal da Paraíba, João Pessoa, PB, Brazil.
authors.forename: Ana Yara
authors.initials: AY
authors.lastname: Gomes
authors.forename: Maria
authors.initials: M
authors.lastname: de Fátima Souza
authors.forename: Steyner F
authors.initials: SF
authors.lastname: Cortes
authors.forename: Virgínia S
authors.initials: VS
authors.lastname: Lemos
mesh_terms: D000818:Animals; D001011:Aorta / Q000187:drug effects / Q000502:physiology; D002217:Carbachol / Q000494:pharmacology; D004338:Drug Combinations; D005260:Female; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects / Q000502:physiology; D066298:In Vitro Techniques; D008297:Male; D019660:Malvaceae / Q000737:chemistry*; D009119:Muscle Contraction / Q000187:drug effects; D010276:Parasympatholytics / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D010840:Phytosterols / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D051381:Rats; D014132:Trachea / Q000187:drug effects / Q000502:physiology; D014315:Triterpenes
chemical_list: D004338:Drug Combinations; D010276:Parasympatholytics; D010840:Phytosterols; D014315:Triterpenes; C007198:cycloleucalenol; D002217:Carbachol; C100089:cycloartenol