Antispasmodic, cardioprotective and blood-pressure lowering properties of Gomphrena perennis L. and its mechanisms of action.

Background: Gomphrena perennis L. is a native plant of South America whose pharmacological properties have not been studied yet. Aim: To evaluate the cardiovascular and intestinal pharmacological effects of Gomphrena perennis L. leaves tincture (GphT) and the mechanisms involved. Experimental procedure: The chromatographic profile of GphT was done. Its ex vivo effects were evaluated by contractile concentration-response curves (CRCs) obtained from the agonist carbachol or calcium found in isolated rat small intestine, as well as in the relaxant CRCs. Cardiac effects were evaluated on isolated rat hearts exposed to ischemia/reperfusion (I/R). Experiments in vivo were performed to evaluate the diuretic activity in conscious rats and the hypotensive effect in anaesthetised rats. Results: Fifteen flavonoids were identified in GphT by HPLC-UV, including diosmin. GphT induced a non-competitive inhibition in both carbachol and calcium CRCs on rat small intestine. The first was not affected by indomethacin. Moreover, GphT, unlike diosmin, relaxed the contracture produced by a high-potassium solution in a dose-dependently way. Neither propranolol nor l-NAME changed it. GphT did not show diuretic activity but induced hypotension insensitive to l-NAME. While GphT perfusion of isolated hearts increased injury consequent to I/R, oral administration was cardioprotective and reversed by l-NAME. However, diosmin did not improve the post-ischemic recovery. Conclusions: This study supports the use of Gomphrena perennis L. tincture as an antispasmodic and hypotensive agent. Moreover, it has been demonstrated to be preventive of post-ischemic cardiac dysfunction. However, diosmin would not be responsible for these effects.

Nebivolol in oral subacute treatment prevents cardiac post-ischemic dysfunction in rats, but hyperthyroidism reduces this protection: mechanisms involved.

Nebivolol could prevent dysfunction in patients suffering myocardial ischemia. However, influence of hyperthyroidism is not known. Consequences and mechanisms of nebivolol treatment were investigated in isolated hearts from euthyroid (EuT) and hyperthyroid (HpT) rats. Rats were orally treated during 1 week with 20 mg/kg/day nebivolol (O-Neb), 30 mg/kg/day atenolol (O-Ate), or not treated (C). Isolated perfused hearts were exposed to global ischemia and reperfusion (I/R) inside a flow calorimeter. Left diastolic ventricular pressure, developed contractile pressure (P), and total heat rate (Ht) were continuously measured, while infarct size was measured after 2-h R. EuT-C and HpT-C hearts developed similarly low post-ischemic contractile recovery and economy (P/Ht). Nebivolol totally prevented dysfunction and reduced infarction size in EuT hearts, but partially improved recovery in HpT rat hearts. Contrarily, oral atenolol totally prevented dysfunction in HpT hearts but partially in EuT hearts. Nebivolol effects were reversed by perfusing L-NAME in both conditions, but partially reduced by aminoguanidine in HpT. However, L-NAME increased P and P/Ht recoveries in EuT-C and HpT-C rat hearts, as well as melatonin. Oral nebivolol prevented post-ischemic dysfunction and infarction in EuT hearts due to adrenergic ß1 blockade and activation of iNOS and/or eNOS, but the effect was attenuated in HpT hearts by excessive iNOS-dependent nitrosative pathways.

Antispasmodic, antidepressant and anxiolytic effects of extracts from Schinus lentiscifolius Marchand leaves.

Schinus lentiscifolius (Anacardiaceae) is widely used in folk medicine for treating gastrointestinal and emotional complaints but there are no scientific studies that support these uses. This work aims at evaluating the antispasmodic and central effects of S. lentiscifolius as well as the flavonoids presence in the tincture (SchT) and the composition of the essential oil (SchO). SchT inhibited the concentration-response curves (CRC) of carbachol and calcium in a non-competitive way in isolated rat intestine, bladder and uterus. SchT also non-competitively inhibited the CRC of histamine in guinea-pig intestine and the CRCs of serotonin and oxytocin in rat uterus. Isoquercetin and rutin were identified in SchT. The behavioral effects of SchT, SchO and infusion of S. lentiscifolius leaves (SchW) were tested in mice. These extracts showed an anxiolytic-like effect in the novelty-suppressed feeding test, which was reversed by flumazenil except in SchO-treated mice. Only SchO reduced the spontaneous locomotor function in the open field test. Also, SchT and SchW decreased immobility time in both, the tail suspension (TST) and forced swimming tests, while SchO produced the same effect in the TST. d-limonene and α-santalol were the main components found in SchO. The results demonstrated that extracts obtained from S. lentiscifolius leaves were effective as intestinal, urinary and uterine antispasmodics. SchT and SchW exhibited anxiolytic and antidepressant properties without sedation, whereas SchO showed also sedative properties. Therefore, the present study gives preclinical support to the traditional use of this plant for gastrointestinal and depressive or emotional symptoms.

Lepidium meyenii (maca) and soy isoflavones reduce cardiac stunning of ischemia-reperfusion in rats by mitochondrial mechanisms.

BACKGROUND AND AIM: Phytoestrogens are traditionally used for cardiovascular risks but direct effects on the ischemic heart remain unclear. Plants with phytoestrogens are used for reducing menopausic symptoms and they could also be cardioprotectives. Here we investigated whether maca (Lepidium meyenii) contains isoflavones and prevents cardiac stunning, in comparison to soy isoflavones. EXPERIMENTAL PROCEDURE: Both products were orally and daily administered to rats during 1 week before exposing isolated hearts to ischemia/reperfusion (I/R). Young male (YM), female (YF) and aged female (AgF) rats treated with maca (MACA, 1 g/kg/day) or soy isoflavones (ISOF, 100 mg/kg/day) were compared to acute daidzein (DAZ, 5 mg/kg i.p.) and non-treated rat groups. Isolated ventricles were perfused inside a calorimeter to simultaneously measure contractile and calorimetrical signals before and during I/R. RESULTS AND CONCLUSIONS: Maca has genistein and daidzein. MACA and ISOF improved the post-ischemic contractile recovery (PICR) and muscle economy (P/Ht) in YM and YF hearts, but not in AgF hearts. DAZ improved PICR and P/Ht more in YM than in YF. The mKATP channels blockade reduced both PICR and P/Ht in DAZ-treated YM hearts, without affecting them in ISOF or MACA-treated YM hearts. In MACA treated YF hearts, the simultaneous blockade of NOS and mKATP channels, or the mNCX blockade reduced cardioprotection. Results show that subacute oral treatment with maca or with soy isoflavones was strongly preventive of cardiac ischemic dysfunction, more than the acute administration of a pure isoflavone (daidzein, genistein). Maca induced synergistic and complex mechanisms which prevented mitochondrial calcium overload.

The mKATP Channels and protein-kinase C Are Involved in the Cardioprotective Effects of Genistein on Estrogen-Deficient Rat Hearts Exposed to Ischemia/Reperfusion: Energetic Study.

Estrogenic deficiency is considered a risk of coronary disease in women. The phytoestrogen genistein could be a safe preventive strategy. The first aim of this work was to validate a model of cardiac stunning in which natural estrogenic deficiency rats, ie, adult young male (YM) and aged female (AgF), are compared with young female rats (YF). The second aim was to study whether the in vivo administration of genistein prevents the stunning in estrogenic deficiency rats. The third aim was to evaluate whether in our estrogenic deficiency model exists a synergy between genistein and estradiol. The fourth aim was to characterize the underlying mechanisms of genistein. Stunning was induced by ischemia/reperfusion (I/R) in isolated hearts inside a calorimeter. The left ventricular pressure (P) and total heat rate (Ht) were simultaneously measured, while diastolic contracture and muscle economy (P/Ht) were calculated. During R, P/Ht and P recovered less in AgF and YM than in YF rat hearts. Genistein through i.p. (GST-ip) improved P and P/Ht in AgF and YM, but not in YF. In YM, the cardioprotections of GST-ip and estradiol were synergistic. After ischemia, GST-ip increased SR Ca leak causing diastolic contracture. The GST-ip cardioprotection neither was affected by blockade of PI3K-Akt, NO synthases, or phosphatases, but it was sensitive to blockade of protein-kinase C and mKATP channels. Results suggest that (1) estrogenic deficiency worsens cardiac stunning, (2) GST-ip was more cardioprotective in estrogenic deficiency and synergistic with estradiol, and (3) cardioprotection of GST-ip depends on the protein-kinase C and mKATP channel pathway activation.

Cardioprotective Mechanisms of Hypothyroidism on Ischemia/Reperfusion in Rats and Effects of Carvedilol: Energetic Study.

Hypothyroidism is considered a cardiac risk factor, but there is controversial evidence about its effects on coronary disease. The aim of this work was to evaluate the influence of hypothyroidism in rat hearts exposed to 2 degrees of stunning due to ischemia and reperfusion (I/R) as well as the underlying mechanisms. Hypothyroid (HypoT) rats were obtained by drinking 0.02% methimazole during 15 days. Isolated hearts were perfused and introduced in a flow calorimeter to measure contractile performance (P), total heat rate (Ht), and muscle economy (P/Ht). Hearts were exposed to 2 models of I/R, moderate and severe (respectively 20 or 30 minutes I/45 minutes R). Moreover, free cytosolic and mitochondrial calcium changes were measured by confocal fluorometry on cardiomyocytes. Comparison to euthyroid (EuT) hearts was done. Hypothyroidism was cardioprotective, but HypoT hearts were more sensitive than EuT hearts to the preischemic blockade of mitochondrial transporters mNCX and mKATP channels. Moreover, the postischemic recovery of P and P/Ht in HypoT hearts was strongly reduced by inhibition of the cellular pathways of PI3K/Akt and protein kinase C (PKC), and it was increased by nitric oxide synthase (NOS) inhibition. However, physiological concentrations of adrenaline reduced the cardioprotection of HypoT, but oral treatment with 20 mg/kg/day carvedilol prevented it. Results show that hypothyroidism reduces the mitochondrial Ca2+ overload during I/R by mKATP channel activation and Ca2+ extrusion through mNCX, while the PI3K/Akt and PKC pathways are involved in that cardioprotection. Contrarily, NOS activation and adrenaline blunt such cardioprotection, but carvedilol prevented the adrenergic dysfunction. These results would explain why hypothyroidism is a clinical risk factor in angor patients under adrenergic exacerbation but reduced the incidence of acute episodes of coronary syndrome in hospitalized patients. Results suggest that a treatment with carvedilol could be a potential therapeutic agent to prevent cardiac postischemic dysfunction in hypothyroid patients.

Ablation of phospholamban rescues reperfusion arrhythmias but exacerbates myocardium infarction in hearts with Ca2+/calmodulin kinase II constitutive phosphorylation of ryanodine receptors.

AIMS: Abnormal Ca2+ release from the sarcoplasmic reticulum (SR), associated with Ca2+-calmodulin kinase II (CaMKII)-dependent phosphorylation of RyR2 at Ser2814, has consistently been linked to arrhythmogenesis and ischaemia/reperfusion (I/R)-induced cell death. In contrast, the role played by SR Ca2+ uptake under these stress conditions remains controversial. We tested the hypothesis that an increase in SR Ca2+ uptake is able to attenuate reperfusion arrhythmias and cardiac injury elicited by increased RyR2-Ser2814 phosphorylation. METHODS AND RESULTS: We used WT mice, which have been previously shown to exhibit a transient increase in RyR2-Ser2814 phosphorylation at the onset of reperfusion; mice with constitutive pseudo-phosphorylation of RyR2 at Ser2814 (S2814D) to exacerbate CaMKII-dependent reperfusion arrhythmias and cardiac damage, and phospholamban (PLN)-deficient-S2814D knock-in (SDKO) mice resulting from crossbreeding S2814D with phospholamban knockout deficient (PLNKO) mice. At baseline, S2814D and SDKO mice had structurally normal hearts. Moreover none of the strains were arrhythmic before ischaemia. Upon cardiac I/R, WT, and S2814D hearts exhibited abundant arrhythmias that were prevented by PLN ablation. In contrast, PLN ablation increased infarct size compared with WT and S2814D hearts. Mechanistically, the enhanced SR Ca2+ sequestration evoked by PLN ablation in SDKO hearts prevented arrhythmogenic events upon reperfusion by fragmenting SR Ca2+ waves into non-propagated and non-arrhythmogenic events (mini-waves). Conversely, the increase in SR Ca2+ sequestration did not reduce but rather exacerbated I/R-induced SR Ca2+ leak, as well as mitochondrial alterations, which were greatly avoided by inhibition of RyR2. These results indicate that the increase in SR Ca2+ uptake is ineffective in preventing the enhanced SR Ca2+ leak of PLN ablated myocytes from either entering into nearby mitochondria and/or activating additional CaMKII pathways, contributing to cardiac damage. CONCLUSION: Our results demonstrate that increasing SR Ca2+ uptake by PLN ablation can prevent the arrhythmic events triggered by CaMKII-dependent phosphorylation of RyR2-induced SR Ca2+ leak. These findings underscore the benefits of increasing SERCA2a activity in the face of SR Ca2+ triggered arrhythmias. However, enhanced SERCA2a cannot prevent but rather exacerbates I/R cardiac injury.

Intestinal, urinary and uterine antispasmodic effects of isoespintanol, metabolite from Oxandra xylopioides leaves.

BACKGROUND: Isoespintanol is a monoterpene isolated from the leaves of Oxandra xylopioides Diels. (Annonaceae) with antioxidant and antiinflammatory effects. It was of interest to know whether it has antispasmodic effects such as other known drugs, phloroglucinol and trimethoxybenzene, used in therapeutics for treating biliary, urinary and uterine spasms. PURPOSE: To assess whether isoespintanol possesses antispasmodic effects on intestine, uterus and bladder. STUDY DESIGN: A preclinical study was performed in which isoespintanol, phloroglucinol and trimethoxybenzene were evaluated with concentration-contractile response curves (CRC) of carbachol in isolated rat intestine and bladder, and with CRC of serotonin (5-HT) in rat uterus. Moreover, it was assessed whether isoespintanol interferes with Ca2+ influx by making CRC of Ca2+ in high-K+ medium in intestine and bladder. RESULTS: Isoespintanol non-competitively inhibited the CRC of carbachol with affinity constant (pK) of 4.78 ±â€¯0.09 in intestine and 4.60 ±â€¯0.09 in bladder. Phloroglucinol and trimethoxybenzene were also non-competitive antagonists, but isoespintanol was 8 times more potent than trimethoxybenzene and similarly potent than phloroglucinol in intestine. In bladder, isoespintanol resulted 8 times more potent than trimethoxybenzene. The maximal inhibition of contraction followed the order of isoespintanol > trimethoxybenzene > phloroglucinol in intestine, and isoespintanol > trimethoxybenzene in bladder. Moreover, isoespintanol also completely and non-competitively inhibited the CRC of Ca2+, with a pK of 5.1 ±â€¯0.1 in intestine, and 4.32 ±â€¯0.07 in bladder. In uterus isoespintanol reduced, completely and non-competitively, the contraction produced by 5-HT with pK of 5.05 ±â€¯0.07. CONCLUSION: Results demonstrate that isoespintanol is a very good intestinal, urinary and uterine antispasmodic, with higher potency than the other drugs used in therapeutics. The mechanism of action of isoespintanol is the interference with Ca2+ influx, at a difference of trimethoxybenzene and phloroglucinol.

Antitussive, antispasmodic, bronchodilating and cardiac inotropic effects of the essential oil from Blepharocalyx salicifolius leaves.

ETHNOPHARMACOLOGY RELEVANCE: Blepharocalyx salicifolius (Kunth) O. Berg (Myrtaceae) is a tree native to Argentina and Uruguay that grows and is cultivated along the riverside of the Rio de la Plata. The leaves of this plant species, locally known as "anacahuita" are used in South America to prepare infusions for the empiric treatment of cough and bronchospasm, as well as diarrhoea and other intestinal disorders. Although previous phytochemical studies have been performed with the essential oil extracted from Blepharocalyx salicifolius, pharmacological evidence supporting its traditional use is still lacking. AIM OF THE STUDY: To experimentally evaluate the pharmacological properties of Blepharocalyx salicifolius based on its traditional use. The studies were performed with tincture (T-Bs) and essential oil (EO-Bs) prepared from its leaves, in isolated rat trachea, intestine and heart preparations. METHODS: The ex-vivo effects of T-Bs and EO-Bs were evaluated with the agonists carbachol (CCh) and calcium chloride (Ca2+) in the contractile concentration-response curves (CRC) of the isolated intestine. The muscle relaxant effect of EO-Bs was evaluated in the isolated trachea and compared with the effect achieved with papaverine as a positive control. The T-Bs and EO-Bs cardiac effects were analysed by perfusion of an isolated rat heart before a period of ischemia/reperfusion (stunning model). The antitussive effect of both T-Bs and EO-Bs was evaluated in mice exposed to ammonia using codeine as a positive control. RESULTS: Both T-Bs and EO-Bs induced a non-competitive inhibition of the CCh-CRC in the rat intestine, with IC50 values of 170.3 ± 48.5µg T-Bs/mL (n = 6) and 5.9 ± 1.6µg EO-Bs/mL (n = 6), respectively. EO-Bs also inhibited non-competitively the Ca2+-CRC, with IC50 value of 1.8 ± 0.3µg EO-Bs/mL (n = 8). A similar effect was obtained with the main active component of the EO-Bs 1,8-cineole. In isolated trachea, EO-Bs induced the relaxation of the CCh-contracted tissue (1.7 ± 0.2µg EO-Bs/mL, n = 11) up to a maximal relaxation that was 1.9 times higher than that of papaverine. In the isolated heart, EO-Bs induced a poor negative inotropic response, and did not improve the contractile and energetic recovery after ischemia and reperfusion. In the mouse cough model, EO-Bs (90mg/Kg) was as effective as codeine (30mg/Kg) in reducing cough frequency. CONCLUSIONS: The results indicate that the preparations from Blepharocalyx salicifolius leaves were effective as central antitussive, bronchodilating and antispasmodic agents, suggestive of a mechanism associated with the inhibition of Ca2+ influx into smooth muscle. The EO-Bs displayed only a poor ability to reduce cardiac inotropism, and was devoid of any cardioprotective properties. Thus, the present study validates the traditional use of this South American plant for asthma, cough and bronchospasm, shedding new light into its potency and putative mechanism of action.

Cardioprotective effect of hyperthyroidism on the stunned rat heart during ischaemia-reperfusion: energetics and role of mitochondria.

NEW FINDINGS: What is the central question of this study? Hyperthyroidism is a cardiac risk factor, but thyroid therapy is used on myocardial stunning. What is the consequence of hyperthyroidism for mitochondrial metabolism and Ca(2+) handling of the postischaemic stunned heart? What is the main finding and its importance? Hyperthyroidism reduced stunning and improved muscle economy of the postischaemic rat heart. The activities of the mitochondrial sodium-calcium exchanger and mitochondrial K(+) channel in hyperthyroid rat hearts were different from those in the euthyroid rat hearts. These findings contribute to the understanding of mitochondrial bioenergetics in pathology and support thyroid therapy in the stunning induced by ischaemia. Transient ischaemia and hyperthyroidism are cardiovascular risk factors. Nevertheless, 3,5,3'-triiodothyronine/thyroxine therapy has been used to revert myocardial stunning. We studied the influence of hyperthyroidism on the role played by mitochondria in myocardial stunning consequent to ischaemia-reperfusion. Rats were injected s.c. daily with 20 µg kg(-1) triiodothyronine for 15 days (HpT group). Isolated ventricles from either HpT or euthyroid (EuT) rats were perfused in a calorimeter, and left intraventricular pressure (in millimetres of mercury) and heat release (Ht; in milliwatts per gram) were measured. Stunning was evoked by 20 min of no-flow ischaemia and 45 min reperfusion. The HpT hearts developed higher postischaemic contractile recovery (PICR) and improved total muscle economy (P/Ht) with lower diastolic contracture (ΔLVEDP) than EuT hearts. Release of Ca(2+) from the sarcoplasmic reticulum during reperfusion with 10 mm caffeine in low-[Na(+) ] Krebs solution evoked a higher contracture in EuT than in HpT hearts. Blockade of the mitochondrial sodium-calcium exchanger with clonazepam increased ΔLVEDP and reduced P/Ht and PICR in HpT but not in EuT hearts. The clonazepam-induced dysfunction in HpT hearts was reduced by ciclosporin, suggesting a dependance on activation of the mitochondrial permeability transition pore. Blockade of the mitochondrial Ca(2+) uniporter with Ru360 reduced P/Ht and PICR to ∼10% in both HpT and EuT hearts. Blockade of mitochondrial K(+) channels with 5-hydroxydecanoate increased LVEDP and reduced PICR and P/Ht in HpT hearts, while it only increased LVEDP in EuT hearts. The results suggest that hyperthyroidism prevents the stunning with high dependence on the mitochondrial sodium-calcium exchanger and mitochondrial K(+) channels. Both HpT and EuT hearts showed a similar and critical role of the uniporter. The HpT hearts have a slow sarcoplasmic reticulum Ca(2+) loss and low mitochondrial Ca(2+) uptake.

Effects of pyruvate on the energetics of rat ventricles stunned by ischemia-reperfusion.

Pyruvate (Pyr) was proposed as an additive to cold high-K(+)-low-Ca(2+) cardioplegia (CPG) to protect the heart during surgery. We explored whether Pyr and CPG would work synergistically to protect rat hearts from stunning during ischemia-reperfusion (I/R). We measured the heat release and contractility of perfused ventricles during I/R, and the cytosolic and mitochondrial [Ca(2+)] in cardiomyocytes by confocal microscopy. We found that under cold-CPG (30 °C), 10 mmol·L(-1) Pyr reduced the post-ischemic contractile recovery (PICR) as well as muscle economy, when added either before ischemia or during I/R, which was reversed by blockade of UCam. In noncardioplegic hearts, Pyr was cardioprotective when it was present during I/R, more so at 37 °C than at 30 °C, with improved economy. In cardiomyocytes, the addition of Pyr to CPG slightly increased the mitochondrial [Ca(2+)] but decreased cytosolic [Ca(2+)]. The results suggest that Pyr only protects hearts from stunning when present before ischemia and during reperfusion, and that it dampens the cardioprotective properties of CPG. The mechanisms underlying such different behavior depend on the dynamic balance between Pyr stimulation of the energetic state and mitochondrial Ca(2+) uptake. Our results support the use of Pyr in stunned hearts, but not in cold high-K(+) cardioplegia.

CARDIAC role of the mitochondrial Ca2+ transporters in the high-[K+](o) cardioprotection of rat hearts under ischemia and reperfusion: a mechano-energetic study.

UNLABELLED: The role of mitochondrial transporters in the cardioprotection of rat hearts exposed to high [K+]-low [Ca2+]-cardioplegia (CPG) and ischemia and reperfusion (I/R) was studied through the mechano-energetic consequences of target drugs. The total heat rate (Ht) and the left intraventricular pressure (LVP) were simultaneously measured in isolated perfused hearts (30 degrees C and 1 Hz) inside a flow-calorimeter during 45 minutes of no-flow I and 45 minutes of R. After stabilization (C) they were pretreated with CPG and 100 microM 5-hydroxidecanoate (5HD, selective mKATP blocker) without and with 10 or 30 microM clonazepam (Clzp, mNCX inhibitor), 30 microM diazoxide (Dzx, selective mKATP opener), 1 microM Ru360 (selective Ca-uniporter blocker), and 0.2 microM cyclosporine-A, (mPTP inhibitor, before I and during R). Before I, 5-hydroxydecanoate in CPG increased the resting heat rate (17.83 +/- 3.55 mW/g) without changing the stunning. Clzp 30 microM + CPG + 5-hydroxydecanoate reduced the postischemic P with diastolic contracture and high Ht. Dzx protected C-hearts from stunning but increased it in CPG hearts with low economy (P/Ht) as well as Ru360. Cyclosporine-A did not modify the stunning of C or CPG ischemic hearts, suggesting that the mPTP was not opened. CONCLUSIONS: Mitochondria have a precise role for determining cardioprotection or stunning in high-K+ cardioplegic rat hearts under I/R. Known protective drugs, such as Dzx and Ru360, which reduce the mitochondrial Ca2+-uptake, increased the stunning of CPG-rat hearts and reduced muscle economy, whereas 5-hydroxydecanoate and Clzp together increased the stunning by inducing mitochondrial Ca2+ overload.

The spasmolytic effect of Aloysia citriodora, Palau (South American cedrón) is partially due to its vitexin but not isovitexin on rat duodenums.

The spasmolytic effects of an acqueous extract of cedrón (AEC) were studied on rat isolated duodenums. This plant (Aloysia citriodora Palau, Verbenaceae) is widely used for gastrointestinal disorders and as eupeptic in South America. AEC non-competitively inhibited the dose-response curve (DRC) of Ach (IC50 of 1.34 +/- 0.49 mg lyophilized/mL) and the DRC of Ca(2+) in high-[K(2-)](o) (IC50 of 2.64 +/- 0.23 mg/mL). AEC potentiated the non-competitive inhibition of either 30 micromol/L W-7 (a calmodulin blocker) and 5-15 micromol/L papaverine on the Ca(2+)-DRC. Also, AEC relaxed the contracture produced by high-[K(+)](o) (IC50 of 2.6 +/- 0.2 mg/mL) until 81.0 +/- 3.2% of the maximal effect of papaverine and 78.1+/- 5.0% of the quercetin, the most selective inhibitor of PDE. The AEC relaxation was non-competitively inhibited by 10-30 micromol/L methylene blue and competitively antagonized by 40 mmol/L TEA. The relaxation of 1mg/mL AEC was inhibited by hypoxia, but not that of 2mg/mL. Two flavonoids were identified by HPLC in the AEC: vitexin and isovitexin. Vitexin non-competitively inhibited the Ach-DRC (pD(2') of 5.7 +/- 0.4) but significantly run leftward the DRC of Ca(2+). Isovitexin did not significantly inhibit the DRC of Ach nor Ca(2+). The results suggest that the spasmolytic effect of AEC could be mostly associated to the increase in cGMP (target shared with the PDE inhibitors) and the activation of K(+)-channels. At low concentrations, AEC also inhibits the aerobic metabolism. The flavonoid vitexin is partially responsible for the effect, since it non-competitively inhibits Ach but not the Ca(2+) influx. Isovitexin was devoid of activity on duodenums.

Cardiotonic and sedative effects of Cecropia pachystachya Mart. (ambay) on isolated rat hearts and conscious mice.

Cecropia pachystachya Mart. is popularly called "ambay" and extensively used in herbal medicine of South America for cough and asthma. In Argentina it grows in neotropical rainforest (Ntr C.p.) and in a temperate region (Tp C.p.). In a previous work we showed their hypotensive properties with different potency and toxicity, and now we studied the Tp C.p. effects in isolated heart from rats and central effects of both plants on the open-field test for mice. Tp C.p. produced a positive inotropic effect on isolated rat hearts, which was not affected by 1 microM propranolol, suggesting that it is not due to a beta-adrenergic effect. In contrast, it was prevented by pretreatment with high [K](o) media, which stimulates the Na,K-ATPase pump, suggesting an inhibition of the pump by "ambay", as digital do. In the open-field test, both Ntr C.p. and Tp C.p. similarly decreased the spontaneous locomotion and exploratory behavior of mice at doses between 180 and 600 mg/kg. Ntr C.p. potentiated the effect of 3 mg/kg diazepam to one similar to 10 mg/kg diazepam, but was not antagonized by 0.5 mg/kg flumazenil. Amphetamine at 5 mg/kg prevented the sedative effect of Ntr C.p. Chromatographic analysis showed that both plants have a qualitatively similar fingerprint but quantitatively differed in at least three components. Although the purpose was not to identify them, both plants have at least 10 compounds. Two of them were in higher amount in Tp C.p. than in Ntr C.p., and then, they could be responsible for the cardiovascular toxicity of Tp C.p. In conclusion, the results suggest that ambay has cardiotonic and sedative properties. The sedative effect could be useful in cough treatment. The extract resulted additive to benzodiazepines but it did not bind to the same site on GABA-A receptor, and it was interfered by the dopamine release produced with amphetamine.