title: Participation of extracellular calcium in α-hederin-induced contractions of rat isolated stomach strips.
abstract: BACKGROUND
  The dry extract of Hedera helix leaves, due to its secretolytic and antispasmodic effects, is commonly used to produce pharmaceuticals applied in case of cough and other respiratory symptoms. The results of some in vitro studies as well as the clinical signs of poisoning caused by Hedera helix suggest however strong contractile effect on smooth muscle. In order to clarify the impact of α-hederin (the main active agent of ivy extract) on smooth muscle, the origin of activated calcium involved in α-hederin-induced contraction of gastric smooth muscle preparations was studied.
  
  
  METHODS
  The study was carried out on rat isolated stomach corpus and fundus strips, under isotonic conditions. The effect of α-hederin (100 μM) on smooth muscle preparations was measured before and after the treatment with verapamil during the incubation in modified Krebs-Henseleit solution (M K-HS). Besides, the effect of saponin was measured during the incubation of preparation in Ca2+-free modified Krebs-Henseleit solution or Ca2+-free EGTA-containing modified Krebs-Henseleit solution.
  
  
  RESULTS
  The obtained results revealed that the application of verapamil significantly inhibited the reaction evoked by α-hederin. The incubation of stomach strips in calcium-free modified Krebs-Henseleit solution did not change the force of the observed contraction in comparison to the reaction of the preparations incubated in regular incubation solution (M K-HS). In contrary, the replacement of M K-HS by calcium-free chelator-containing solution inhibited totally the reaction to α-hederin.
  
  
  CONCLUSIONS
  The results indicated that α-hederin-induced contraction results from the influx of calcium which is located in intercellular spaces or bound to the outside of the cell membrane. The Ca2+ influx occurs predominantly through voltage-dependent calcium channels of L-type.
authors.affiliation: Warsaw University of Life Sciences, Faculty of Veterinary Medicine, Department of Preclinical Sciences, Division of Pharmacology and Toxicology, 8 Ciszewskiego Street, 02-786 Warsaw, Poland. marta_mendel@sggw.pl
authors.forename: Marta
authors.initials: M
authors.lastname: Mendel
authors.forename: Magdalena
authors.initials: M
authors.lastname: Chłopecka
authors.forename: Natalia
authors.initials: N
authors.lastname: Dziekan
authors.forename: Wojciech
authors.initials: W
authors.lastname: Karlik
authors.forename: Maria
authors.initials: M
authors.lastname: Wiechetek
mesh_terms: D000818:Animals; D002118:Calcium / Q000502:physiology*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects* / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects* / Q000502:physiology; D009828:Oleanolic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D012503:Saponins / Q000494:pharmacology*; D013270:Stomach / Q000187:drug effects* / Q000502:physiology; D014700:Verapamil / Q000494:pharmacology
chemical_list: D002121:Calcium Channel Blockers; D012503:Saponins; C010177:beta-hederin; D009828:Oleanolic Acid; D014700:Verapamil; D002118:Calcium