Participation of extracellular calcium in α-hederin-induced contractions of rat isolated stomach strips.

ETHNOPHARMACOLOGICAL RELEVANCE: 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. MATERIALS AND 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.

The effect of the whole extract of common ivy (Hedera helix) leaves and selected active substances on the motoric activity of rat isolated stomach strips.

ETHNOPHARMACOLOGICAL RELEVANCE: The long tradition of using the dry extract of Hedera helix (common ivy) leaves in traditional and contemporary alternative medicine caused that many biological and pharmacological studies have been aimed at evaluating the effects of ivy. Some of the results suggest that Hedera helix extract possesses bronchodilatatory and antispasmodic activity. On the other hand, the symptoms of ivy intoxication in human and animals, as well as adverse-reactions observed during the therapy with ivy-based pharmaceuticals, indicate rather stimulant effect of the plant on smooth muscle. Thus, the aim of this study was to evaluate the effect of two main active substances extracted from the plant (α-hederin and hederacoside C) and the whole dry extract of Hedera helix on the gut motility. MATERIALS AND METHODS: The experiments were carried out on isolated stomach corpus and fundus strips. The tissues were isolated from rats. The experiments were performed in isotonic conditions. The results are expressed as the percent of the reaction caused by a reference contractile substance, acetylcholine. RESULTS AND CONCLUSIONS: The obtained results revealed that α-hederin applied in the concentration ranged from 25 to 320µM significantly changed the spontaneous motoric activity of rat stomach smooth muscle. The observed reaction had always the same character, a contraction, and its force was concentration dependent. The second tested saponin, hederacoside C, did not alter the motility of rat isolated stomach corpus and fundus strips when administered in the concentration up to 100 µM, however, if applied in the concentration of 350 µM it induced a remarkable concentration of smooth muscle. Eventually, the whole extract of Hedera helix in a dose containing 60 µM of hederacoside C produced a strong contraction which strength was comparable with the reaction generated by acetylcholine. According to the results, it is very likely that α-hederin, but not hederacoside C contributes to the contractile response of isolated stomach corpus and fundus strips to the application of Hedera helix leaves' extract.