Contractile Effects Research Articles

The Role of Reactive Oxygen Species in the Regulation of Blood Vessel Tone in Perinatal and Early Postnatal Ontogenesis

Reactive oxygen species (ROS) have been considered for many years as negative regulators in the cardiovascular system. Indeed, excessive production of ROS characterizes many cardiovascular diseases. The damaging effect of ROS can be especially pronounced in a newborn organism, since during this period their contractile effect in pulmonary arteries remains as high as in the pre-term fetus arteries and the antioxidant systems have not yet formed. Therefore, in the first hours and days of independent life, pulmonary arteries tend to contract, primarily due to the low bioavailability of endothelial NO, which increases the risk of developing pulmonary hypertension in newborns. At the same time, during the perinatal period, ROS play an important role in the adaptive reactions of the circulatory system. ROS provide occlusion of the ductus arteriosus and separation of the pulmonary and systemic circulations soon after birth, and also contribute to the contraction of peripheral vessels during hypoxia, which often accompanies the delivery, and therefore provide priority blood supply to the brain in these conditions. The vasomotor effect of ROS is also pronounced in early postnatal ontogenesis, but it has a different character. In the first weeks of life, the action of ROS serves as one of the mechanisms for increasing endothelium-dependent relaxation of pulmonary vessels. In addition, during early postnatal ontogeny, ROS may play an important role in the regulation of systemic vascular tone. This review outlines the current understanding of the vasomotor role of ROS in the vessels of the pulmonary and systemic circulation and considers the mechanisms of ROS effects on the functioning of vascular endothelial and smooth muscle cells in the perinatal and early postnatal periods.

Practical Effect of Cervical Softening Decoction Combined with Delivery Ball Approach in Promoting Vaginal Delivery in Primiparous Women

In Traditional Chinese Medicine, Cervical Softening Decoction is derived from a modified “Wan Bing Hui Chun” formulation and consists of natural herbal ingredients such as Angelica sinensis, Ligusticum chuanxiong, Leonurus heterophyllus, and Cortex Daphnes. The decoction regulates Qi, promotes blood circulation, and facilitates fetus descent. Genkwanin is an active compound in L. heterophyllus and previous studies identified this compound in ethanolic extracts from rat uterine smooth muscle cell membrane fractions. To further understand the pharmacological activities of Cervical Softening Decoction, we examined genkwanin effects on isolated rat uterine contractions and protein expression in rat tissue with postpartum hemorrhage complicated by multiple organ dysfunction syndrome (MODS). We also explored the practical effects of Cervical Softening Decoction combined with a birthing ball approach on promoting natural delivery in primiparous women. First, an isolated rat uterine smooth muscle contraction model was generated and three groups established: oxytocin group (0.002 U/mL), conventional genkwanin dose group (3 μg/mL), and high genkwanin dose group (6.0 μg/mL). Changes in uterine smooth muscle contraction and relaxation amplitudes were recorded before and after administration. Second, 50 rats were used to establish the following groups: (1) control group, (2) postpartum hemorrhage with MODS model group (MODS group), and (3) a postpartum hemorrhage with MODS treated with genkwanin group (genkwanin group). Western blotting was used to detect and compare tumor necrosis factor-α (TNF-α) and interleukin (IL)-6 protein expression levels in lung tissue from groups. Finally, 84 primiparous women admitted to our hospital between January 2020 and December 2021 were selected and divided into two groups based on their obstetric interventions. The control group (n = 42) received routine obstetric intervention, while the observation group (n = 42) received Cervical Softening Decoction and delivery ball interventions. Delivery conditions were compared across groups. In basic studies, genkwanin doses significantly increased contraction and relaxation values in isolated rat uterine smooth muscle (P <0.05). Moreover, the genkwanin contractile effects at conventional and high doses were comparable with oxytocin. TNF-α and IL-6 protein expression in MODS group lung tissue was significantly higher when compared with the control group, while expression in the genkwanin group was significantly reduced when compared with the MODS group (P <0.05). In clinical studies, the observation group showed significantly higher natural delivery rates and Labor Agentry Scale (LAS) scores when compared with the control group. In contrast, cesarean section rates, first and second stage labor duration, total labor duration, and Facial Pain Scale (FPS) scores were significantly lower in the observation group when compared with the control group (P <0.05). In basic studies, genkwanin elicited significant contraction effects on isolated rat uterine smooth muscle and effectively inhibited inflammatory responses in rats with postpartum hemorrhage complicated by MODS. In clinical studies, combined Cervical Softening Decoction and delivery ball generated promising practical effects in promoting vaginal delivery in primiparous women. The intervention significantly increased the probability of a natural delivery, shortened labor duration, relieved maternal pain, and enhanced maternal control during delivery.

Abstract 14259: Contractile Effects of Glucagon in Atrial Preparations From Transgenic Mice and Men

Glucagon, a peptide composed of 29 amino acids, produced mainly in the pancreas can also stimulate cardiac function. Glucagon might contribute to hyperglycemia in diabetes mellitus type 2 and is thus of clinical relevance. There is controversy in the literature whether glucagon affects force and beating rate in the human atrium and which receptor is involved. Hence, we studied the effect of glucagon on atrial preparations of wild type mouse hearts (WT), from transgenic mice with cardiac overexpression of the human glucagon receptor (GR-TG) and for comparison in human right atrial preparations. We noted that glucagon exerted concentration- and time-dependent positive chronotropic effects in atrial preparations from WT and GR-TG starting at 0.1 nM glucagon and amounting to 25 % of pre-drug value at 3 nM glucagon (n=8, p<0.05). These effects were antagonized by the glucagon receptor antagonist SC203973 (1 μM), the inhibitor of cAMP dependent protein kinase H89 (1 μM), by the M-cholinoceptor agonist 1 μM carbachol, by the A1-adenosine receptor antagonist R-phenylisopropyladenosine (1 μM) and the inhibitors of hyperpolarization-activated cyclic nucleotide gated channels namely ivabradine (1 μM) or cesium chloride (2 mM) (n=5-6, p<0.05). In left atrial preparations from GR-TG but not WT, glucagon exerted starting at 1 nM a positive inotropic effect. Interestingly, in human atrial preparations glucagon at 1 μM in the additional presence of the phosphodiesterase III inhibitor cilostamide (1 μM) increased force of contraction by 34 % (n=5, p<0.05). We conclude that glucagon can exert contractile effects in mammalian hearts via GR, but they exhibit considerable regional and species differences. The physiological and therapeutic relevance of glucagon in the human heart needs to be fully elucidated.

Smooth muscle contraction of the fundus of stomach, duodenum and bladder from mice exposed to a stress-based model of depression

Several reports have demonstrated that depressive disorder is related to somatic symptoms including gastrointestinal or genitourinary alterations. The pathophysiological mechanisms underlying the gastrointestinal or genitourinary alterations associated with the depression are still not fully understood. Therefore, this study aimed to evaluate the motor activity of gastrointestinal (fundus of stomach and duodenum) and genitourinary tract (bladder) in a stress-based animal model of depression. Adult male mice were submitted to uncontrollable and unpredictable stress (learned helplessness model), controllable stress and non-stressful situations (control). Then, animals were euthanized and the fundus of stomach, duodenum segments or whole bladder were isolated and mounted in a standard organ bath preparation. We evaluated the contractile effects induced by KCl 80 mM for 5 min or carbachol (acetylcholine receptor agonist). The relaxant effects of isoproterenol (β-adrenoceptor agonist) were also checked. Animals submitted to the learned helplessness model developed a helpless (depressive-like behavior) or resilient (does not exhibit depressive-like behavior) phenotype. The contractions induced by carbachol were diminished in fundus of stomach isolated from helpless and resilient animals. The isoproterenol-induced fundus of stomach relaxation was reduced in resilient but not helpless mice. The contractions/relaxation of duodenum segments isolated from helpless or resilient animals were not altered. Both helpless and resilient animals showed an increase in the bladder contractions induced by carbachol while the relaxant effects of isoproterenol were reduced when compared to control. Conversely, mice underwent a controllable stress situation did not exhibit alterations in the fundus of stomach or duodenum contraction/relaxation induced by pharmacological agents although a decrease in the bladder contraction induced by carbachol was found. In conclusion, incontrollable and unpredictable stress and not depressive phenotype (helpless animals) or controllable stress could be related to the alterations in motor activity of the fundus of stomach and bladder.

Glucagon and Its Receptors in the Mammalian Heart.

Glucagon exerts effects on the mammalian heart. These effects include alterations in the force of contraction, beating rate, and changes in the cardiac conduction system axis. The cardiac effects of glucagon vary according to species, region, age, and concomitant disease. Depending on the species and region studied, the contractile effects of glucagon can be robust, modest, or even absent. Glucagon is detected in the mammalian heart and might act with an autocrine or paracrine effect on the cardiac glucagon receptors. The glucagon levels in the blood and glucagon receptor levels in the heart can change with disease or simultaneous drug application. Glucagon might signal via the glucagon receptors but, albeit less potently, glucagon might also signal via glucagon-like-peptide-1-receptors (GLP1-receptors). Glucagon receptors signal in a species- and region-dependent fashion. Small molecules or antibodies act as antagonists to glucagon receptors, which may become an additional treatment option for diabetes mellitus. Hence, a novel review of the role of glucagon and the glucagon receptors in the mammalian heart, with an eye on the mouse and human heart, appears relevant. Mouse hearts are addressed here because they can be easily genetically modified to generate mice that may serve as models for better studying the human glucagon receptor.

Abstract P1170: Changes In Endothelin Signaling In A Long-term Rat Coronary Culture Resembles Chronic Coronary Syndrome

Background: Coronary artery disease generates changes in the structure and function of the blood vessels. 48hrs organ culture (mimicking the acute loss of blood flow) of coronary arteries induces the upregulation of contractile endothelin type B (ETB) receptors, resembling the pattern seen in ischemic heart disease. MEK inhibitors (U0126 and Trametinib), can acutely inhibit the upregulation of these receptors, illustrating the importance of this pathway. The 48hrs organ culture model has been proven successful for translation in acute ischemic disease, but arterial changes have not been studied in a long-term chronic model which could be important for chronic coronary syndrome. Purpose: 1) Investigate the changes of ETB receptors after incubation in a long-term optimized medium for organ culture, mimicking the reduction of blood flow in chronic coronary syndrome and 2) determine whether Trametinib, would have treatment effect on the upregulation of ETB receptors in both long term and short term culture. Methods: Rat coronary arteries were incubated in organ culture for 48hrs in DMEM ± trametinib (“acute”) or in a long-term optimized medium for organ culture for 14 days (“chronic”). After the incubation, arteries were mounted stainless steel wires (40 μm) on a Mulvany-Halpern arterial wire myograph and cumulative concentration response curves were made to measure arterial contractility to the ETB receptor specific agonist Sarafotoxin (S6c). Trametinib was added at time 0 (for both the acute and chronic organ culture) or 7 days delayed. Results: For the “acute” culture, we observed a high contractile effect in response to S6c (Emax=136.5±18%). The presence of Trametinib greatly reduced this contractile effect (Emax=10±1.9%) and arteries were comparable to fresh (Emax=0.8±0.7%). The rat coronary arteries in the “chronic” culture maintained their ability to contract in response to potassium, and S6c had a strong contractile effect (Emax=74.64±17%). Interestingly, neither trametinib addition at time 0 nor at day 7 could inhibit the functional upregulation of ETB in the chronic model. Conclusion: Chronic coronary syndrome may require new inhibitors of ETB receptor upregulation. This could be investigated with our new long-term rat coronary artery model.

An Exploratory Study on the Contractile Effects of Hydroxy-α-Sanshool and Hydroxy-β-Sanshool, the Active Ingredients of Daikenchuto, on the Internal Anal Sphincter.

Daikenchuto (DKT) enhances the contraction of the internal anal sphincter (IAS) in patients with constipation and fecal incontinence; however, the mechanism of its action is unknown. We investigated the effects of the active ingredients of DKT (hydroxy-α-sanshool (HAS) and hydroxy-β-sanshool (HBS)) on the contractile activity of the canine rectum and IAS. Three male beagle dogs were prepared for each of the HAS, HBS, and control groups. Force transducers were attached to the rectal and IAS surfaces of the dogs, and the contractile responses were measured by telemetry under conscious conditions. HAS (10 mg/body) and HBS (2.5 mg/body) were administered intrarectally at doses previously identified from an effective dose of DKT extract (1.5 g/body), and contractile responses were recorded up to 6 h after administration. Contractile activity of the rectum and IAS was evaluated by observing the area under the curve (AUC) of the recorded contraction waveform. Plasma concentrations of HAS and HBS were measured before and after administration to confirm IAS exposure to both ingredients. The mean AUC values of the IAS for the control, HAS, and HBS groups at 10 min after administration were 115, 87, and 220 (g-min), respectively, indicating a higher contraction in the HBS group, which was maintained for approximately 3 h. As for the rectum, no contractile response was observed in either the HAS or HBS groups. Plasma concentrations of both ingredients peaked at 20 min after administration. HBS could be involved in the contractile action of DKT on the IAS.

Pharmacological Basis for Antispasmodic, Bronchodilator, and Antidiarrheal Potential of Dryopteris ramosa (Hope) C. via In Vitro, In Vivo, and In Silico Studies.

Background:Dryopteris ramosa is used as an old treatment for several diseases. D. ramose fronds are eaten to treat gastrointestinal (GIT) issues and as an antibiotic. However, there is a dearth of literature justifying its traditional use. Aims and objectives: the current work used biological and molecular docking studies to support traditional usage and elucidate D. ramosa's multitarget mechanism. Materials and methods: Bioactive compounds were docked in silico. Force displacement transducers coupled with a power lab data gathering system examined the effects of compounds on rabbit jejunum, trachea, and aorta tissues. Albino mice and rats were used for in vivo studies. Results: Bioactive compounds interacted with inflammation, asthma, and diarrhea genes, according to in silico studies. D. ramosa crude extract (Dr.Cr) calmed impulsive contractions and K+ (80 mM)-provoked contractions in the jejunum and tracheal tissue dose-dependently, showing the presence of the Ca++ channel-blocking (CCB) effect, further verified by the rightward parallel shift of CRCs equivalent to verapamil. Polarity-based fractionation showed spasmolytic activity in Dr.DCM and muscarinic receptors mediated spasmogenic activity in the Dr.Aq fraction. Dr.Cr vasoconstricted the aortic preparation, which was totally blocked by an angiotensin II receptor antagonist. This suggests that Dr. Cr's contractile effect is mediated through angiotensin receptors. In rats and mice, it showed anti-inflammatory and antidiarrheal action. Conclusion: This study supports the traditional medicinal uses of D. ramosa against GIT disorders and may be an important therapeutic agent in the future.

Lysergic acid diethylamide stimulates cardiac human H2 histamine and cardiac human 5-HT4-serotonin receptors

Lysergic acid diethylamide (LSD) is an artificial hallucinogenic drug. Thus, we hypothesized that LSD might act 5-HT4 serotonin receptors and/or H2 histamine receptors. We studied isolated electrically stimulated left atrial preparations, spontaneously beating right atrial preparations, and spontaneously beating Langendorff-perfused hearts from transgenic mice with cardiomyocyte-specific overexpression of the human 5-HT4 receptor (5-HT4-TG) or of the H2-histamine receptor (H2-TG). For comparison, we used wild type littermate mice (WT). Finally, we measured isometric force of contraction in isolated electrically stimulated muscle strips from the human right atrium obtained from patients during bypass surgery. LSD (up to 10 µM) concentration dependently increased force of contraction and beating rate in left or right atrial preparations from 5-HT4-TG (n = 6, p < 0.05) in 5-HT4-TG atrial preparations. The inotropic and chronotropic effects of LSD were antagonized by 10 µM tropisetron in 5-HT4-TG. In contrast, LSD (10 µM) increased force of contraction and beating rate in left or right atrial preparations, from H2-TG. After pre-stimulation with cilostamide (1 µM), LSD (10 µM) increased force of contraction in human atrial preparations (n = 6, p < 0.05). The contractile effects of LSD in human atrial preparations could be antagonized by 10 µM cimetidine and 1 µM GR 125487. LSD leads to H2-histamine receptor and 5-HT4-receptor mediated cardiac effects in humans.

Methamphetamine increases force of contraction in isolated human atrial preparations through the release of noradrenaline

We measured the cardiac contractile effects of the sympathomimetic amphetamine-like drug methamphetamine alone and in the presence of cocaine or propranolol in human atrial preparations. For a more comprehensive analysis, we also examined the effects of methamphetamine in preparations from the left and right atria of mice and, for comparison, analyzed the cardiac effects of amphetamine itself. In human atrial preparations, methamphetamine and amphetamine increased the contractile force, the relaxation rate, and the rate of tension development, and shortened the time to maximum tension and the time to relaxation. Likewise, in mice preparations, methamphetamine and amphetamine increased the contractile force in the left atrium and increased the beating rate in the right atrium. The effect in human atrial preparations started at 1 µM, therefore methamphetamine was less effective and potent than isoproterenol in increasing contractile force. These positive inotropic effects of methamphetamine were greatly attenuated by 10 µM cocaine and abolished by 10 µM propranolol. The inotropic effects of methamphetamine in human atrial preparations were associated with, and are believed to be mediated at least in part by, an increase in the phosphorylation state of the inhibitory subunit of troponin. In conclusion, the sympathomimetic central stimulant drug methamphetamine (as well as amphetamine) increased contractile force and protein phosphorylation, presumably through a release of noradrenaline in isolated human atrial preparations. Thus, methamphetamine acts as an indirect sympathomimetic in the human atrium.

OR-1896 increases force of contraction in the isolated human atrium

OR-1896 ((R)-N-(4-(4-methyl-6-oxo-1,4,5,6-tetrahydropyridazin-3-yl)phenyl)acetamide) is the main active metabolite of levosimendan. However, nobody has reported a positive inotropic effect of OR-1896 in isolated human cardiac preparations. The mechanism of action of OR-1896 remains controversial. Hence, we wanted to know whether OR-1896 exerts a positive inotropic effect in humans and what might be the underlying mechanism. Therefore, we measured the contractile effects of OR-1896 (0.01–10 µM cumulatively applied) in isolated electrically stimulated (1 Hz) human right atrial preparations (HAP) obtained during cardiac surgery. OR-1896, given alone, exerted time- and concentration-dependent positive inotropic effects; 1-µM OR-1896 increased force by 72 ± 14.7% (p < 0.05, n = 6) and shortened the time of relaxation by 10.6 ± 3.6% (p < 0.05, n = 11) in HAP started at 0.1 µM, plateaued at 1-µM OR-1896, and was antagonized by 1-µM propranolol. The maximum positive inotropic effect of OR-1896 in human right atrial preparations was less than that of 10-µM isoprenaline. EMD 57033 (10 µM), a calcium sensitizer, enhanced the force of contraction further in the additional presence of 1-µM OR-1896 by 109 ± 19% (p < 0.05, n = 4). Cilostamide (10 µM), an inhibitor of phosphodiesterase III given before OR-1896 (1 µM), blocked the positive inotropic effect of OR-1896 in HAP. Our data suggest that OR-1896 is, indeed, a positive inotropic agent in the human heart. OR-1896 acts as a PDE III inhibitor. OR-1896 is unlikely to act as a calcium sensitizer in the human heart.

Essential oil of Sicilian Prangos ferulacea (L.) Lindl. and its major component, β−ocimen, affect contractility in rat small and large intestine

Ethnopharmacological relevancePrangos ferulacea (L.) Lindl is an Apiaceae plant, widely used in traditional medicine. Recently, chemical composition and biological activities of its essential oil (Prangroil) have been reported, but there are no studies on possible effects on intestinal contractility. Aims of the studyWe investigated the effects of essential oil Sicilian Prangoil on the contractility of rat small (duodenum) and large (colon) intestine and the related action mechanism. Materials and methodsResponses to Prangoil and to its major component β−ocimen in intestinal segments were assessed in vitro as changes in isometric tension. ResultsPrangoil, induced in duodenum, depending upon doses, contraction and/or muscular relaxation. Instead, in colon Prangoil only reduced the phasic contractions and induced muscular relaxation. β−ocimen, in both segments, produced only reduction of the spontaneous contractions without affecting basal tone. Prangoil contractile effects were abolished by ω-conotoxin, neural N-type Ca2+ channels blocker, atropine, muscarinic receptor antagonist, neostigmine, acetylcholinesterase (AChE) inhibitor, suggesting that Prangoil-induced contraction would be the result of an increase in neuronal cholinergic activity. Prangoil and β−ocimen inhibitory effects were unaffected by ω−conotoxin, L-NAME, blocker of the NO synthase, ODQ, soluble guanylate cyclase inhibitor, excluding involvement of neurotransmitter release or NO synthesis in the inhibitory effects. Potassium channel blocker did not affect Prangoil or β-ocimen inhibitory responses. Prangoil or β-ocimen inhibited the Ca2+ and high-KCl solution -induced contractions and the Carbachol-induced contractions in calcium free solution. ConclusionPrangoil affects the contractility of small and large intestine in rat, with regional differences, via potentiation of neural cholinergic activity, blockade of L-type voltage-gated calcium channel and reduction of Ca2+ release from the intracellular store. The Prangroil main components, β−ocimen, contributes to the inhibitory effects.

PO-02-206 A MECHANISM FOR PACING-INDUCED REGIONAL CONTRACTILE DYSFUNCTION MEDIATED BY RELEASED CATECHOLAMINES

We have previously shown that non-excitatory epicardial stimulation (NES) increases measures of cardiac function mediated by local release of norepinephrine. In this further investigation we focused on the effects of NES on the local myocardial contractile pattern. Farm pigs were anesthetized and instrumented with a LV high-fidelity pressure/volume conductance transducer, thoracic aortic pressure transducer, left atrial (LA)/ LV epicardial electrodes, and sonomicrometer segment length (SL) gauges placed proximal (lateral base) and distal (posterior mid LV) to the LV stimulation site. During constant LA pacing, LV pulses (0.8ms, 2-3x threshold volts) were applied during the absolute refractory period before and after β-receptor blockade (BB, metoprolol). Regional contractile function was analyzed by constructing LVP vs. SL loops in a beat-by-beat fashion thus allowing characterization of local cardiac function in relation to LV pressure over the entire cardiac cycle. NES resulted in a local contractile dysfunction characterized by an early shortening, subsequent lengthening, and re-shortening pattern during the cardiac cycle in the SL gauge proximal (middle tracing), but not remote to the stimulation site (bottom tracing). The onset of early lengthening in the proximal SL coincided with peak pressure generation, followed by re-shortening as LV pressure fell. The LVP vs. SL loop was markedly altered. This contractile effect rapidly waned within 10-15 seconds after cessation of electrical stimulation and was abolished by BB. The NES induced dysfunction developed within an average of 5-10 seconds of stimulation onset and was accompanied by increases in several global indices of cardiac function (dP/dt, peak LVP, early aortic valve opening) which were also abrogated by B-blockade. These findings demonstrate that pacing elicits local catecholamine release that may cause dyssynergy and mimic the regional pacing-induced contractile dysfunction seen at pacing sites in man.

Comparing the effects of chemical Ca2+ dyes and R-GECO on contractility and Ca2+ transients in adult and human iPSC cardiomyocytes

We compared commonly used BAPTA-derived chemical Ca2+ dyes (fura2, Fluo-4, and Rhod-2) with a newer genetically encoded indicator (R-GECO) in single cell models of the heart. We assessed their performance and effects on cardiomyocyte contractility, determining fluorescent signal-to-noise ratios and sarcomere shortening in primary ventricular myocytes from adult mouse and guinea pig, and in human iPSC-derived cardiomyocytes. Chemical Ca2+ dyes displayed dose-dependent contractile impairment in all cell types, and we observed a negative correlation between contraction and fluorescence signal-to-noise ratio, particularly for fura2 and Fluo-4. R-GECO had no effect on sarcomere shortening. BAPTA-based dyes, but not R-GECO, inhibited in vitro acto-myosin ATPase activity. The presence of fura2 accentuated or diminished changes in contractility and Ca2+ handling caused by small molecule modulators of contractility and intracellular ionic homeostasis (mavacamten, levosimendan, and flecainide), but this was not observed when using R-GECO in adult guinea pig left ventricular cardiomyocytes. Ca2+ handling studies are necessary for cardiotoxicity assessments of small molecules intended for clinical use. Caution should be exercised when interpreting small molecule studies assessing contractile effects and Ca2+ transients derived from BAPTA-like chemical Ca2+ dyes in cellular assays, a common platform for cardiac toxicology testing and mechanistic investigation of cardiac disease physiology and treatment.

Contractile effect of trimethylamine and trimethylamine-n-oxide on isolated human umbilical arteries.

The aim of this study is to investigate the effect of trimethylamine (TMA) and trimethylamine-n-oxide (TMAO) on the contractility of human umbilical artery and the possible mechanisms involved. Vasoactive responses to TMA and TMAO on human umbilical artery rings were measured in isolated organ baths. Cumulative dose-response curves for TMA and TMAO were obtained before and after incubation with atropine, yohimbine, prazosin, indomethacin, verapamil, and Ca+2 -free Krebs-Henselite solution. Administration of cumulative TMA and TMAO resulted in dose-dependent contraction at concentrations ranging from 10 to 100 mM on human umbilical artery rings. TMA-induced contractions were more potent than TMAO-induced contractions (TMA: -logEC50 = 1.00 ± 0.02, TMAO: -logEC50 = 0.57 ± 0.02). Contraction responses to TMA were significantly lower in the presence of verapamil and in the absence of external Ca+2 (p < 0.001, p < 0.05, respectively). Our results showed that TMA and TMAO caused vasoconstriction in isolated human umbilical artery rings. Our findings also indicated that TMA but not TMAO-induced vasoconstriction was partially dependent on extracellular Ca2+ and calcium influx through L-type Ca2+ channels. Our results suggest that TMA and TMAO may have the potential to contribute to cardiovascular diseases through their direct effect on vascular contractility in human arteries.

Antagonistic effect of mepyramine and tubocurarine on the histamine-mediated contraction of intestinal smooth muscle cells

Introduction: Histamine is an endogenous ligand which exerts its biological actions by binding to 4 subtypes of histamine receptors (HR). Its effects on the gastrointestinal tract are complex being the dominant effect contraction of muscle cells.&#x0D; Method: The aim of this study was to verify the antagonistic effect of mepyramine (10-10M - 10-7M) and tubocurarine (10-7M - 10-4M) in the contractile action of histamine (10-11M - 10-4M). in guinea pig ileum, for this purpose it was used the program Virtual Organ Bath 16 V 2.8, which allow quantify the change in strength(g) produced by smooth muscle contraction in the presence of these substances. Concentration-response curves were obtained through GraphPad Prism® graphic program. The determination of the competitive nature of the antagonist and the calculation of the affinity constant was performed through Schild method.&#x0D; Results: Mepyramine is a competitive antagonist of histamine (10-10M to 10-7M), making it a potential therapeutic agent for the treatment of irritable bowel syndrome. On the other hand, it is not understood that tubocurarine is an antagonist of histamine receptors.&#x0D; Conclusions: The results obtained provide evidence that the contractile effect of histamine on the smooth muscle of intestinal cells isolated from guinea pig is competitively antagonized by mepyramine. In addition, by calculating the pKB parameter, it was found that this compound has greater potency than other antihistamines.

Effects of histamine on the contractility of the rat distal cauda epididymis

The motor activity of the epididymis duct is an essential process for male fertility and it is regulated by hormonal, neuronal and epithelial mechanisms. However, although there is evidence for the presence of histamine in the epididymis, its effects on epididymal motor activity are unknown. This study sought to evaluate the contractile effects of histamine on the rat distal cauda epididymis duct. Segments of the distal cauda epididymis duct from male Wistar rats were isolated and used in isolated organ bath experiments to evaluate the contractile effects of histamine in the absence or presence of antagonists of histamine receptors, α1-adrenoceptors and muscarinic acetylcholine receptors. The effects of histamine on noradrenaline induced contractions were also investigated. Histamine was able to induce phasic contractions on rat distal cauda epididymis duct which were prevented by promethazine 10–1000 nM (H1 receptor antagonist), ranitidine 1–100 μM (H2 receptor antagonist), atropine 100 nM (muscarinic antagonist), and prazosin 100 nM (α1-adrenoceptor antagonist). In addition, histamine was also able to modify noradrenaline-induced contractions possibly via activation of H1 and H2 receptors. In conclusion, this study demonstrates that histamine can induce phasic contractions of rat distal cauda epididymis via H2 receptors and autonomic neurotransmitters. Histamine may also exert modulatory actions on contractions of rat distal cauda epididymis duct induced by adrenergic receptor agonists. Further studies are necessary to unveil the localization of histamine receptors within the epididymal duct and the consequences of manipulation of the histaminergic system on epididymal function and male fertility.

Chemical characterization, antimicrobial activity and cardiac effects in rat heart of the ethyl acetate fraction of Syzygium cumini (L.) Skeels

Plants are important sources of secondary metabolites responsible for various biological activities. In this research, was evaluated the effect action ethyl acetate fraction of Syzygium cumini leaves (Sc-AcOEt) in the antimicrobial activity, contractile and electrical effects in isolated rat hearts and the chemical characterization. Antimicrobial activity was assessed using the disk-diffusion method and the determination of the minimum inhibitory concentration. The contractile and electrical effects were tested using the Langendorf method. The chemical characterization was evaluated through quantification and HPLC analyzes. P. aeruginosa was not viable in any concentration of the fraction (MIC 0,125 mg/mL), while S. aureus showed a MIC of 0.5 mg/mL. K. pneumoniae and E. coli had the highest MIC (1 mg/mL). A reduction in LVDP was observed after heart perfusion with 0.1 mg/mL of Sc-AcOEt. No change was observed in the duration of systole and diastole at all concentrations and in the electrocardiographic parameters. Total phenols, total flavonoids and total flavonols contents of Sc-AcOEt, calculated from the respective calibration curves, were 21.556µg/mg AGE, 617.222µg/mg QE and 315,222µg/mg RE, respectively. In addition, the HPLC analysis of Sc-AcOEt showed the presence of gallic acid, quercetin-3-glucoside, naringin and myricetin as main components. Thus, the Sc-AcOEt has important antimicrobial and cardiac activities possibly due to its chemical constituents.

Effects of aqueous ginger extract on smooth muscle contraction in bovine cecum: in vitro study.

Intestinal hypomotility cause health risks and economic losses and is considered as an important digestive disorder that efforts to find prokinetic drugs can solve this major problem. This study investigated the effects of Zingiber officinale aqueous extract (ZOAE) on caecal smooth muscle contractions in healthy cows. To perform in vitro tests, cecum strips connected to the organ bath. Ginger aqueous extract caused concentration-dependent contraction in caecal smooth muscle with an effective threshold concentration of 6.00 mg L-1. The strongest contraction was caused at a concentration of 100 mg L-1 with an average contraction of 141%. To evaluate the possible mechanisms underlying the contractile effect on cecum strips, atropine, 1,1-dimethyl-4-diphenylacetoxypiperidinium iodide (4-DAMP) and verapamil completely inhibited aqueous extract induced smooth muscle contractions, while addition of hexamethonium had no effect on the contraction process. The lack of reduction of contractions caused by the extract in the presence of hexamethonium indicates that presence of acetylcholine-like constituents independent of nicotinic receptors. The inhibitory properties of atropine and 4-DAMP indicate that at least part of the prokinetic effect of the extract is due to stimulating the muscarinic receptors, especially M3 receptors. Also, verapamil inhibitory function proves that the extract acting by L-type calcium channels. The results suggest that the ZOAE has a potential prokinetic effect which may provide a pharmacological base to its medicinal or prophylactic use in caecal motility disorders.

Evaluation of the vasorelaxant effect of Sugammadex on the arterial smooth muscle in rats

Although NMBAs (Neuro Muscular Blocking Agents) have been used for a long time, postoperative residual curarization is still a significant problem. Nowadays, an agent named Sugammadex is used for the reversal of curarization. It has been presented as a safer agent than its predecessor, neostigmine. The main purpose of this study is to investigate the effects of Sugammadex on rat thoracic aorta and enlighten the mechanism of action and potential benefits in surgical operations with general anesthesia. Twenty Wistar albino rats were used for the experiments. Thoracic aorta segments have been removed and mounted to the organ bath. Contraction and relaxation responses were presented as a percentage of phenylephrine (3x10-5 M) contraction. After recording contractile responses of Sugammadex (10-8-10-4 M), relaxation responses of Sugammadex (10-8-10-4 M) have been recorded both in the presence and absence of L-NAME (3x10-5 M) (Potent Nitric Oxide Sentase Inhibitor). Finally, relaxation responses of sugammadex-rocuronium have been recorded. Sugammadex caused slightly noticeable and concentration-dependent contraction on isolated thoracic aorta strips. Sugammadex also caused potent and concentration-dependent relaxation on isolated rat thoracic aorta. The relaxation response caused by Sugammadex has been diminished significantly in the presence of L-NAME. Administration of rocuronium with Sugammadex did cause neither relaxation nor any additional contractile effect on isolated rat thoracic aorta strips. Sugammadex is a promising agent in reversing rocuronium-induced neuromuscular block. Although the adverse effects of this agent are not studied in detail, it seems Sugammadex is safer than neostigmine. The side effects of anesthetic agents are one of the main problems of surgical procedures, including neurosurgery, gynecology, and obstetrics. Especially acute hypotension may be fatal in neurosurgery and gynecological operations. Sugammadex should be used carefully in adjusted and individualized doses to avoid hypotension-related adverse effects.