Effects of Oleamide on the Vasomotor Responses in the Rat.

Introduction: Cardiovascular effects of endocannabinoids (eCBs) have generated considerable interest since it has been suggested that the eCB system could become the new pharmacological target, either by blocking its activity or by promoting its effects on several cardiovascular diseases such as hypovolemic and septic shock or hypertension. The purpose of this study was to examine the effects of oleamide on several vasomotor responses in adult rats. Materials and Methods: Blood pressure (BP) was measured both directly and indirectly. Coronary flow was quantified with Langendorf preparation, and the vasomotor responses induced by oleamide were analyzed in the aortic rings. Results: Oleamide induced a decrease in BP, by both direct and indirect methods, which were dose dependent. An increase in coronary flow was observed with Langendorf preparation depending on the dose. Oleamide produced a vasodilator response in aortic rings pre-contracted with phenylephrine (10-5 M), which was concentration and endothelium dependent. This relaxing effect was of minor magnitude than that induced with the same dose on BP. L-NAME did not modify these effects. However, indomethacin induced a shift to the left of the concentration-response curve to oleamide and an increase in the magnitude of maximum vasodilation in rings with endothelium. Oleamide produced the maximal relaxant response at 10-5 M concentration. Conclusions: Oleamide has both in vivo and in vitro vasodilator effects. Vasodilator effects could be mediated by compounds synthesized/released by the endothelium (hyperpolarizing factor) or acting directly on vascular smooth muscle in aortic rings. The TRPV1 and CB1R receptors could mediate these effects. Finally, the results suggest that oleamide probably induces the synthesis/release of a vasoconstrictor prostanoid.

Synthesis of ranolazine derivatives containing the (1S,4S)-2,5-diazabicyclo[2.2.1]heptane moiety and their evaluation as vasodilating agents.

Two diazabicyclic analogues of ranolazine, (S,S,S)-5 and (S,S,R)-5, and their epimeric mixture were synthesized. Furthermore, their vasomotor effects on rat aorta rings precontracted with phenylephrine were analyzed. These compounds showed vasodilating effects significantly greater than ranolazine. The vasodilating activities of these analogues have two components, one that depends on the endothelium, due to the release of NO, and another one due to a direct effect on the vascular smooth muscle. The compounds [(S,S,S)(S,S,R)]-5 and (S,S,R)-5 induce, in a manner similar to ranolazine, the release of a prostanoid from the cyclooxygenase pathway, whose vasoconstrictor effect is masked by the predominant vasodilation induced by these compounds.

Effects of ranolazine on vasomotor responses of rat aortic rings.

BACKGROUND AND AIMS: Ranolazine is a piperazine derivative that was approved in 2006 for the treatment of chronic stable angina. Compared with first-line drugs currently used to treat angina, beneficial effects of ranolazine occur without changing hemodynamic parameters such as heart rate and blood pressure. In the present study the effects of ranolazine on vasomotor responses of rat aortic rings were examined. METHODS: Pharmacological evaluation was performed by analyzing the vasomotor responses of ranolazine on aortic rings of adult male Wistar rats precontracted with phenylephrine (10(-5) M). In each experiment we used a pair of rings (with and without endothelium) from the same aorta and superfused in the same bath. RESULTS: Ranolazine (10(-6)-10(-4) M) induced a concentration-dependent relaxation of phenylephrine-precontracted rings. The relaxation was only partially dependent on the presence of the endothelium (56.78 ± 6.81% in rings with endothelium and 47.88 ± 4.70% in rings without endothelium). In rings with endothelium, L-NAME induced a shift to the right of the concentration-response curve to ranolazine. Blocking the cyclooxygenase pathway induced a leftward shift of the concentration relaxation curve to ranolazine in both types of rings and increased the ranolazine-induced relaxation in rings without endothelium. CONCLUSIONS: Ranolazine has a vasodilatory effect that is predominantly endothelium-independent. The synthesis/release of nitric oxide by the endothelium may, however, contribute to its relaxing action. These effects of ranolazine may contribute to its beneficial effects in patients with stable angina.

Isolated aorta model and its contribution to phytopharmacology / Modelo de aorta aislada y su contribución a la fitofarmacología

Since the early 50's until now the isolated thoracic aorta has been a traditional and productive model for pharmacological studies. This experimental model has been closely related to Doctor Robert Furchgott's research. The discovery of the role of endothelium in the vasorelaxation induced by acetylcholine (ACh), represented a milestone in biological sciences and also had an important consequence on the isolated aorta preparation. In this work, we describe the isolated aorta technique and the improvements made in Doctor Penna's laboratory at Facultad de Medicina, Universidad de Chile, as well as the Mexican contribution. Since endothelium plays a key role on vascular relaxation and its dysfunction is one of first indicators (biomarker) of cardiovascular diseases, the isolated aorta model is a valuable preparation. Considering the great amount of phytochemical present in many natural sources, like vegetables, fruits and medinal plants, we expect this model to continue delivering significant contributions to the knowledge in pharmacology and phytopharmacology.

Desde principios de los años 50 hasta ahora la aorta torácica aislada ha sido un modelo tradicional y productivo para estudios farmacológicos. Este modelo experimental ha estado estrechamente relacionado con la investigación realizada por el Doctor Robert Furchgott. El descubrimiento de la función del endotelio en la vasodilatación inducida por la acetilcolina (ACh), representó un hito en las ciencias biológicas y también tuvo una consecuencia importante en la preparación de aorta aislada. En este trabajo se describe la técnica de aorta aislada y las mejoras realizadas en el laboratorio del Doctor Penna en la Facultad de Medicina, Universidad de Chile, así como la contribución de investigadores mexicanos. Puesto que el endotelio juega un papel clave en la relajación vascular y su disfunción es uno de los primeros indicadores (biomarcadores) de enfermedad cardiovascular, el modelo de aorta aislada es una valiosa preparación. Teniendo en cuenta la gran cantidad de fitoquímicos presentes en muchas fuentes naturales como verduras, frutas y plantas medicinales, podemos esperar que este modelo continúe entregando importantes aportes al conocimiento en farmacología y fitofarmacología.

Effects of the chronic ingestion of an infusion of Ruta chalepensis on the vasomotor responses of rat aortic rings / Efectos de la ingestión crónica de una infusión de Ruta chalepensis sobre las respuestas vasomotoras de anillos de aorta de rata

Ruta chalepensis, is used, in traditional medicine, as emmenagogue, abortive, and analgesic. We analyzed, in male Wistar rats, the effects of the chronic intake of an infusion of Ruta chalepensis (20 g/L) on the vasomotor responses of, either intact or endothelium-denuded aortic rings, to phenylephrine or carbachol. Only in rings with endothelium significant effects were observed. The infusion induced a leftward shift of the concentration-response curve to phenylephrine and an increase in maximal tension development. These effects were abolished by indomethacin. In these rings, inhibiting the synthesis of nitric oxide, in the presence of indomethacin, induced a leftward shift of the concentration response curve to phenylephrine, as well as an increase in maximal tension. These results suggest that the chronic ingestion of a Ruta chalepensis infusion induces an endothelium dependent increase in the synthesis/release of cyclooxygenase-dependent vasoconstrictor prostanoids, and an increase in the basal synthesis/release of nitric oxide.

Ruta chalepensis se utiliza en la medicina tradicional como emenagogo, abortivo y analgésico. Se analizaron, en ratas Wistar macho, los efectos de la ingesta crónica de una infusión de Ruta chalepensis (20 g /L), sobre las respuestas vasomotoras de anillos de aorta con y sin endotelio, a la fenilefrina o al carbacol Se observaron efectos significativos sólo en anillos con endotelio. La infusión indujo un desplazamiento a la izquierda de la curva de concentración-respuesta a fenilefrina y un incremento en la tensión máxima desarrollada. Estos efectos fueron abolidos por la indometacina. La inhibición de la síntesis de óxido nítrico, en presencia de indometacina, produjo un desplazamiento a la izquierda de la curva de concentración-respuesta a la fenilefrina, así como un incremento en la tensión máxima. Estos resultados sugieren que la ingesta crónica de una infusión de Ruta chalepensis induce un incremento en la síntesis/liberación de prostanoides vasoconstrictores dependientes de la ciclooxigenasa y un aumento en la síntesis /liberación basal de óxido nítrico.

The Respiratory Exchange Ratio is Associated with Fitness Indicators Both in Trained and Untrained Men: A Possible Application for People with Reduced Exercise Tolerance.

BACKGROUND: The respiratory exchange ratio (RER) indirectly shows the muscle's oxidative capacity to get energy. Sedentarism, exercise and physically active lifestyles modify it. For that reason, this study evaluates the associations between RER during sub-maximum exercise and other well established fitness indicators (body fat, maximum heart rate, maximum O(2) uptake, workload, and lactate threshold), in physically active trained and untrained men. METHODS: The RER, O(2) uptake and blood lactate were measured in eight endurance trained and eight untrained men (age, 22.9 ± 4.5 vs. 21.9 ± 2.8 years; body mass, 67.1 ± 5.4 vs. 72.2 ± 7.7 kg; body fat, 10.6 ± 2.4% vs. 16.6 ± 3.8% and maximum O(2) uptake, 68.9 ± 6.3 vs. 51.6 ± 5.8 ml•kg(-1)•min(-1)), during maximum exercise test and during three different sub-maximum exercises at fixed workload: below, within or above the lactate threshold. RESULTS: Endurance trained men presented higher O(2) uptake, lower blood lactate concentrations and lower RER values than those in untrained men at the three similar relative workloads. Even though with these differences in RER, a strong association (p < 0.05) of RER during sub-maximum exercise with the other well established fitness indicators was observed, and both maximum O(2) uptake and lactate threshold determined more than 57% of its variance (p < 0.05). CONCLUSIONS: These data demonstrate that RER measurement under sub-maximum exercise conditions was well correlated with other established physical fitness indicators, despite training condition. Furthermore, the results suggest that RER could help obtain an easy approach of fitness status under low exercise intensity and could be utilized in subjects with reduced exercise tolerance.

Protective effect of Arthrospira maxima on fatty acid composition in fatty liver.

BACKGROUND: Arthrospira maxima has been widely used for nutritional purposes. Additionally, A. maxima has shown immunomodulator, antiviral, antioxidant, vasomotor and hypolipidemic effects in laboratory and animal studies. A. maxima prevents fatty liver induced by either carbon tetrachloride (CCl4) or fructose-rich diet; however, the liver lipid composition in these models is not clearly known yet. The aim of this study was to evaluate the effects of A. maxima on the liver lipid profile in CCl4-induced steatohepatitis. METHODS: A single sublethal, intraperitoneal dose of CCl4 was administered to male Wistar rats fed a diet with or without 5% A. maxima. Liver lipids: total lipids, triacylglycerols, total cholesterol, free fatty acids, and thiobarbituric acid reactive substances were assessed 24 and 48 h after injury with CCl4. Additionally, triacylglycerols, total cholesterol and aspartate aminotransferase were evaluated in blood. RESULTS: Forty eight hours after CCl4 treatment, rats fed a diet without A. maxima had serum aspartate aminotransferase and liver triacylglycerols values that were, respectively, 2.2 and 1.4 times higher than those of animals receiving 5% A. maxima in their diet. The same pattern was observed for liver free fatty acids and thiobarbituric acid reactive substances. The groups fed a diet with A. maxima and treated with CCl4 showed a higher saturated fatty acid liver content than the groups without A. maxima in their diet. The percentage of unsaturated fatty acids increased 48 h after CCl4 treatment, but its value was 0.5 times lower in the group receiving A. maxima than in the group fed without A. maxima. In the liver, all animals receiving A. maxima showed a trend towards a lower percentage of unsaturated fatty acids, despite the mentioned increase 48 h after CCl4 treatment. CONCLUSIONS: The results suggest that, in the fatty liver induced by CCl4, the hepatoprotective effect of A. maxima involves (a) an antioxidant mechanism and (b) a lower unsaturation of the liver fatty acids. The preventive effect of A. maxima on the liver lipid changes induced by CCl4 could be partially explained by its antioxidant action and the ability to increase the synthesis/release of nitric oxide, but not by its soluble dietary fiber.

Ethanolic extract of Spirulina maxima alters the vasomotor reactivity of aortic rings from obese rats.

BACKGROUND: Aortic rings with endothelium excised from fructose-fed obese rats develop more tension in response to phenylephrine and relax less in response to carbachol than corresponding rings from lean rats. This altered vascular reactivity is prevented when Spirulina maxima is added to the fructose-rich diet. In the present study the effects of a raw ethanolic extract of Spirulina maxima on the vasomotor responses of aorta rings from sucrose-fed obese hypertensive rats were analyzed. METHODS: The experiments were performed on aorta rings from sucrose-fed obese male rats. For each experiment, a pair of rings from the same aorta (one with intact endothelium, the other without a functional endothelium) was used. In this study we analyzed, in vitro, the effects of the ethanolic extract of Spirulina maxima on the reactivity of the aortic rings to phenylephrine and to carbachol. RESULTS: On rings with endothelium, the extract produced the following effects: a) a concentration-dependent (0.06-1.0 mg/mL) decrease of the contractile response to phenylephrine; b) a rightward shift and a decrease in maximal developed tension, of the concentration-response curve to phenylephrine; c) a concentration-dependent relaxation of phenylephrine-precontracted rings. These effects persisted in the presence of indomethacin but were prevented by L-NAME. The extract had no effect on the concentration-response curve of phenylephrine-precontracted rings to carbachol. On endothelium-denuded rings the extract caused a significant rightward shift of the concentration response curve to phenylephrine without any effect on maximal tension development. CONCLUSIONS: These results suggest that, in rings from obese rats, the extract, in addition to increasing the synthesis/release of NO, also inhibits the synthesis/release of a cyclooxygenase-dependent vasoconstrictor metabolite of arachidonic acid, which is increased in obesity.

Design and synthesis of novel biologically active thrombin receptor non-peptide mimetics based on the pharmacophoric cluster Phe/Arg/NH2 of the Ser42-Phe-Leu-Leu-Arg46 motif sequence: platelet aggregation and relaxant activities.

The identification of the thrombin receptor has promoted the interest for the development of new therapeutic agents capable of selectively inhibiting unwanted biological effects of thrombin on various cell types. In this study we have designed and synthesized two series of new thrombin receptor antagonists based on the thrombin receptor motif sequence S42FLLR46, one possessing two (Phe/Arg) pharmacophoric groups and the other possessing three (Phe/Arg/NH2). N-(6-Guanidohexanoyl)-N'-(phenylacetyl)piperazine (1), N-(phenylacetyl)-4-(6-guanidohexanoylamidomethyl)piperidine (2), and N-(phenylacetyl)-3-(6-guanidohexanoylamido)pyrrolidine (3) (group A) carry the two pharmacophoric side chains of Phe and Arg residues incorporated on three different templates (piperazine, 4-aminomethylpiperidine, and 3-aminopyrrolidine). Compounds with three pharmacophoric groups (group B) were built similarly to group A using the same templates with the addition of an extra methylamino group leading to (S)-N-(6-guanidohexanoyl)-N'-(2-amino-3-phenylpropionyl)piperazine (4), (S)-N-(2-amino-3-phenylpropionyl)-4-(6-guanidohexanoylamidomethyl)piperidine (5), and (S)-N-(2-amino-3-phenylpropionyl)-3-(6-guanidohexanoylamido)pyrrolidine (6). Compounds were able to inhibit thrombin-induced human platelet activation even at low concentrations. In particular, among compounds in group A, compound 3 was found to be the most powerful thrombin receptor activation inhibitor, showing an IC50 of approximately 0.11 mM on platelet aggregation assay. Among compounds in group B, compound 4 was the most powerful to inhibit thrombin-induced platelet aggregation, showing an IC50 of approximately 0.09 mM. All compounds were also found to act as agonists in the rat aorta relaxation assay. Interestingly, the order of potency of these compounds as agonists of the endothelial thrombin receptor was the inverse of the order of potency of the same compounds as antagonists of the platelet thrombin receptor. Such compounds that are causing vasodilation while simultaneously inhibiting platelet aggregation would be very useful in preventing the installation of atherosclerotic lesions and deserve further investigation as potential drugs for treating cardiovascular diseases. The above findings coupled with computational analysis molecular dynamics experiments support also our hypothesis that a cluster of phenyl, guanidino, and amino groups is responsible for thrombin receptor triggering and activation.