Consumption of a Byproduct of Chia Seed Oil Extraction by Cold Pressing Ameliorates Cardiovascular Risks Factors in an Experimental Model of Metabolically Unhealthy Normal Weight.

The byproduct of Salvia hispanica (chia) seed oil extraction by cold pressing, also known as expeller, possesses a high nutritional value. It is rich in proteins, fibers, minerals, and has a residual oil content of 7-11%, which is rich in omega 3 linolenic acid (ALA). However, this byproduct has been historically undervalued. Thus, the aim of current work was to study the effects of consuming of a rich in chia expeller diet on a rabbit model of metabolically unhealthy normal weight to validate their use as a functional food. Rabbits were fed different diets for a period of 6 weeks: a standard diet (CD), a high-fat diet (HFD), a rich in expeller CD (Exp-CD) and a rich in expeller HFD (Exp-HFD). The Exp-HFD attenuated the rise in basal glucose, TyG index, triglycerides, cholesterol and non-HDL cholesterol induced by the HFD. Both rich in expeller diets reduced mean arterial blood pressure (MAP) and increase liver and fat ALA levels compared to their respective controls. Furthermore, the angiotensin converting enzyme (ACE) activity was lower in the lungs of animals fed on rich in expeller diets compared to their respective controls. In vitro studies showed that ALA inhibited ACE activity. The evaluation of vascular reactivity revealed that rich in expeller diets improved angiotensin II affinity and reduced contractile response to noradrenaline. In conclusion, the consumption of rich in expeller diets showed beneficial effects in preventing cardiovascular risk factors such as insulin resistance, dyslipidemia and MAP. Therefore, its use as functional ingredient holds significant promise.

A Flavonoid-rich Zuccagnia punctata Extract Prevents High Fat Diet-induced Normal Weight Obesity in a Rabbit Model.

Oral administration of rich in flavonoids hydroalcoholic extract from Zuccagnia punctata (ZpE) improves lipid profile and prevents vascular dysfunction in hypercholesterolemic rabbits. This study aimed to evaluate the ability of ZpE to prevent metabolic and vascular alterations induced by high fat diet (HFD) on a metabolically obese and normal weight rabbit model. The major components of ZpE were analyzed by HPLC method. Rabbits were separated into six groups: 1-fed on standard chow (CD); 2-fed on HFD; 3, 4, 5- fed on HFD and orally administrated 2.5 mg, 5 mg or 10 mg GAE/day of ZpE, respectively (ZpE- HFD); 6- fed on HFD and orally administered 30 mg orlistat/day (Or-HFD). All diets were administrated by 6 weeks. The major compounds of ZpE identified were chalcones: 2',4'-dihydroxy-3'-methoxychalcone and 2',4'-dihydroxychalcone. Oral treatment with ZpE 5 mg GAE/day as well as orlistat prevented the HFD-induced increase of triglycerides, fasting glucose, intraperitoneal glucose test, white cells, and TyG index. Acetylcholine relaxation was reduced in arteries from HFD group and oral administration of ZpE reached this response to CD values. Contractile response to angiotensin II was lower in arteries from rabbits fed on HFD treated with ZpE 5 and 10 mg GAE/day than those of untreated rabbits. Moreover, ZpE could inhibit the activity of pancreatic lipase in vitro and in vivo. In conclusion the ZpE may prevent normal weight obesity by inhibiting the pancreatic lipase. Thus, the use of ZpE as a natural product in the prevention of metabolic syndrome and endothelial dysfunction is very promising.

Effects of Cold Pressed Chia Seed Oil Intake on Hematological and Biochemical Biomarkers in Both Normal and Hypercholesterolemic Rabbits.

Most of the studies on the beneficial effects of chia have been conducted with its seeds. There is less evidence about the effects of cold pressed chia seeds oil on hypercholesterolemia-induced alterations. Thus, this study investigated the effects of cold pressed chia seed oil supplementation on certain hematological and biochemical biomarkers in both normal and hypercholesterolemic rabbits. Thirty two male rabbits were assigned to four different groups and fed on: 1) a regular diet (CD), 2) CD supplemented with 10% chia oil, 3) CD supplemented with 1% cholesterol, 4) CD supplemented with 1% cholesterol and 10% chia oil. After six weeks of dietary interventions, mean arterial blood pressure and visceral fat were measured and blood samples were analyzed for lipid profiles and hematological parameters while erythrocyte membranes and retroperitoneal fat were analyzed for fatty acids composition and biochemical biomarkers. Dietary intervention with chia oil achieved control of the hypercholesterolemia-induced increase of mean arterial blood pressure, neutrophil to lymphocytes ratio, erythrocyte membrane fluidity, and improved erythrocyte morphological alterations. With regard to inflammatory biomarkers, chia oil supplementation reduced omega-6/omega-3 polyunsaturated fatty acids ratios and arachidonic/linolenic fatty acids ratios both in erythrocytes and fat from normal and hypercholesterolemic rabbits. The increase of linolenic fatty acid into the retroperitoneal fat was about 9 times higher than its respective controls. These results provide support for the potential health benefits of chia oil intake on hypercholesterolemia-associated clinical, hematological and biochemical alterations.

Prosopis alba seed flour improves vascular function in a rabbit model of high fat diet-induced metabolic syndrome.

AIMS: Prosopis alba flour is a natural source of nutrient and phytochemicals with potential effects on cardiovascular risk factors. The aim of this work was to examine the effects of dietary supplementation with Prosopis alba seed flour (Pr-Feed) on a high fat diet (FD)-induced rabbit model of metabolic syndrome. MAIN METHODS: Rabbits were separated in four groups: fed regular diet (CD); CD supplemented with Pr-Feed; fed on 18 % FD; FD supplemented with Pr-Feed. All diets were administrated for 6 weeks. After the feeding period body weights, mean blood pressure, heart rate and visceral abdominal fat (VAF) were determined; glucose tolerance test (GTT) was performed; total cholesterol (TC), HDL-cholesterol, LDL-cholesterol, triglycerides (TG), fasting glucose (FG), aspartate amino transferase, alanine amino transferase, bilirubin and creatinine were measured in serum. Abdominal aorta was excised and vascular function was assessed by acetylcholine relaxation and contractile response to KCl, norepinephrine and angiotensin II. KEY FINDINGS: Phytochemical analyses showed that the main compounds of Pr-Feed were apigenin C-glycosides. FD increased VAF, FG, TG, reduced HDL-cholesterol and induced abnormal GTT. Pr-Feed addition to FD did not modify these alterations. Aortic rings from rabbits fed on FD exhibited an impaired relaxation-response to acetylcholine and increased agonist vasoconstrictor responses. Pr Feed-supplemented FD improved the response to acetylcholine, and prevented the increase of the contractile response to KCl, norepinephrine and angiotensin II. SIGNIFICANCE: Results suggest that dietary supplementation with Pr-Feed, rich in apigenin C-glycosides, has vascular protector properties and could be used to prevent vascular alterations characterizing the metabolic syndrome.

Oral administration of Zuccagnia punctata extract improves lipid profile, reduces oxidative stress and prevents vascular dysfunction in hypercholesterolemic rabbits.

BACKGROUND: The consumption of flavonoids has been shown to prevent cardiovascular diseases including atherosclerosis. In this sense, in a recent in vitro study we demonstrated that a rich in flavonoids extract from Zuccagnia punctata has beneficial effects on vascular function in aorta from hypercholesterolemic rabbits. PURPOSE: The aim of this study was to evaluate the ability of a hydroalcoholic extract from Z.puncata (ZpE) to prevent alterations induced by high cholesterol diet in rabbits. METHODS: The major components of the ZpE, flavonoids, were analyzed by using a validated reversed phase HPLC method. Rabbits were separated in five groups: fed standard chow (CD); CD orally administrated 2.5 mg, 5 mg or 10 mg GAE/day ZpE (ZpE- CD); fed 1% cholesterol-enriched chow (HD); HD orally administrated 2.5 mg GAE/day ZpE (ZpE-HD); HD orally administrated 2.5 mg rosuvastatin/day (Ro-HD). All diets were administrated by 6 weeks. Body weights (BW), mean blood pressure (MAP), heart rate (HR), visceral abdominal fat (VAF), organ weight (heart, kidney, liver) and vascular morphology were determined. Total cholesterol (TC), triglycerides (TG), fasting glucose (FG), aspartate amino transferase (AST), alanine amino transferase (ALT), bilirubin, creatinine, thiobarbituric acids reactive substances (TBARS) and glutathione reduced/oxidized index were measured in serum. Abdominal aorta was excised and vascular function was assessed by acetylcholine and sodium nitroprusiate relaxation and contractile response to norepinephrine and angiotensin II. RESULTS: The major compounds of ZpE identified were chalcones: 2',4'-dihydroxy-3'-methoxychalcone and 2',4'-dihydroxychalcone. Oral treatment with ZpE reduced MAP, TC, TG, TBARS, aortic intima/media ratio and increased glutathione reduced/oxidized index in HD rabbits. No differences were found in AST, ALT, bilirubin or creatinine. Acetylcholine relaxation was normalized and contractile response to norepinephrine and angiotensin II was reduced in ZpE-HD. CONCLUSION: Oral administration of ZpE as natural product in the prevention of cardiovascular disease related with hypercholesterolemia and endothelial dysfunction is very promising.

High fat diet-induced metabolically obese and normal weight rabbit model shows early vascular dysfunction: mechanisms involved.

BACKGROUND: Obesity contributes significantly to the development and evolution of cardiovascular disease (CVD) which is believed to be mediated by oxidative stress, inflammation and endothelial dysfunction. However, the vascular health of metabolically obese and normal weight (MONW) individuals is not completely comprehended. OBJECTIVES: The purpose of our study was to evaluate vascular function on the basis of a high fat diet (HFD)-MONW rabbit model. SUBJECTS: Twenty four male rabbits were randomly assigned to receive either a regular diet (CD, n = 12) or a high-fat diet (18% extra fat on the regular diet, HFD, n = 12) for 6 weeks. RESULTS: Body weight, TBARS and gluthathione serum levels were similar between the groups; fasting glucose, triglycerides, C reactive protein (CRP), visceral adipose tissue (VAT), triglyceride-glucose index (TyG index) were higher in the HFD group. Compared to CD, the HFD rabbits had glucose intolerance and lower HDL-cholesterol and plasma nitrites levels. Thoracic aortic rings from HFD rabbits exhibited: (a) a reduced acetylcholine-induced vasorelaxation; (b) a greater contractile response to norepinephrine and KCl; (c) an improved angiotensin II-sensibility. The HFD-effect on acetylcholine-response was reversed by the cyclooxygenase-2 (COX-2) inhibitor (NS398) and the cyclooxygenase-1 inhibitor (SC560), and the HFD-effect on angiotensin II was reversed by NS398 and the TP receptor blocker (SQ29538). Immunohistochemistry and western blot studies showed COX-2 expression only in arteries from HFD rabbits. CONCLUSIONS: Our study shows a positive pro-inflammatory status of HFD-induced MONW characterized by raised COX-2 expression, increase of the CRP levels, reduction of NO release and oxidative stress-controlled conditions in an early stage of metabolic alterations characteristic of metabolic syndrome. Endothelial dysfunction and increased vascular reactivity in MONW individuals may be biomarkers of early vascular injury. Therefore, the metabolic changes induced by HFD even in normal weight individuals may be associated to functional alterations of blood vessels.

Stearoyl-CoA desaturase indexes and n-6/n-3 fatty acids ratio as biomarkers of cardiometabolic risk factors in normal-weight rabbits fed high fat diets.

BACKGROUND: Biomarkers for cardiometabolic risk (CMR) factors would be important tools to maximize the effectiveness of dietary interventions to prevent cardiovascular diseases. Thus, the aim of this work was to analyze stearoyl-CoA desaturase (SCD) indexes and n-6/n-3 fatty acids (FA) ratio as biomarkers of CMR induced by feeding rabbits on high fat diets (HFDs). METHODS: Rabbits were fed either regular diet or 18 % fat in regular diet (HFD) or 1 % cholesterol diet (HD) or diet containing 1 % cholesterol and 18 % fat (HFD-HD) during 6 weeks. Body weights (BW), blood pressure, visceral abdominal fat (VAF) and glucose tolerance test were determined. Total cholesterol (TC), low density lipoprotein-cholesterol (LDL-C), high density lipoprotein-cholesterol (HDL-C), triglycerides (TG), fasting glucose (FG), and FA levels from plasma were measured. SCD indexes were calculated as product/precursor ratios of individual FA. RESULTS: BW was similar in all diet groups. HD increased TC, LDL-C, HDL-C, and TG. HFD increased TG, VAF and FG, and decreased HDL-C. The addition of HFD to HD joined to dyslipidemia increased VAF and FG. SCD indexes were increased and n-6/n-3 was unchanged in HD. SCD indexes were reduced and n-6/n-3 FA ratio was increased in HFD and HFD-HD. CMR factors were correlated positively with n-6/n-3 FA ratio. Although VAF had a stronger correlation with n-6/n-3 FA ratio than with SCD indexes, VAF was associated independently to both markers. CONCLUSIONS: HFD simulating lipid composition of the average Western-style diet induced experimental rabbit models of normal-weight metabolic syndrome (MS). SCD indexes and n-6/n-3 were modified according to the type of dietary fat. Considering that VAF and CMR factors appear to be stronger associated to n-6/n-3 FA ratio than to SCD indexes, n-6/n-3 FA ratio may be a better biomarker of MS and CMR in normal-weight subjects than SCD indexes.

The role of oxidative stress in alterations of hematological parameters and inflammatory markers induced by early hypercholesterolemia.

AIMS: The investigation of the effects of a high cholesterol diet (HD) for a short-time period on hematological parameters and the potential role of oxidative stress and inflammation markers. MAIN METHODS: Rabbits were fed either a control diet or a diet containing 1% cholesterol (HD) for 5-6 weeks. The plasma lipid levels, C reactive protein (CRP), total red blood cells (RBC), total white blood cells (WBC), platelet count, packed cell volume (PCV) and leukocyte formula were determined. Oxidative stress was evaluated by the thiobarbituric acid reactive substances (TBARS), total glutathione and GSH serum level measurements. The osmotic fragility and the membrane fluidity of erythrocytes were determined. The levels of total cholesterol and TBARS were also measured in the erythrocyte membrane suspension. KEY FINDINGS: A decrease in the RBC and PCV was observed in rabbits fed on HD. The membrane rigidity and osmotic fragility were increased, and the morphological changes caused by the HD and TBARS levels in the erythrocyte membrane may account for this phenomenon. The inflammatory markers as the CRP levels, the platelet count, the WBC and the neutrophils were increased. The TBARS and GSH levels in the serum were increased and decreased, respectively. SIGNIFICANCE: This study shows that feeding rabbits an HD for a short time induces hematological alterations, disturbances in the oxidant-antioxidant balance and an increase of inflammatory markers. These findings support the importance of the early correction or prevention of high cholesterol levels to disrupt the process leading to the development of cardiovascular diseases.

17-Octadecynoic acid improves contractile response to angiotensin II by releasing vasocontrictor prostaglandins.

The present study investigated the role of CYP-enzymes in the modulation of vasoconstrictor responses to angiotensin II in rabbit aortae. In arteries with the endothelium-intact (E+) the CYP-inhibitor, 17-octadecynoic acid (17 ODYA), increased the efficacy to angiotensin II (17-ODYA-effect) as well as simultaneous incubation with miconazole (epoxygenase-inhibitor) and CAY 10434 (ω-hydroxylase-inhibitor). The removal of endothelium (E-) caused potentiation of the 17 ODYA-effect. Therefore, endothelium-dependent and -independent mechanisms would be involved. 17-ODYA and miconazole reduced Ach-relaxation. Indomethacin blocked the 17-ODYA-effect in E+ and E- arteries but blunted the response to angiotensin II only in E+ arteries. NS 398 (cyclooxygenase-2-inhibitor) blocked the 17-ODYA-effect and reduced angiotensin II affinity as well as SQ 29548 (thromboxane-prostanoid (TP) receptor-inhibitor). In E- arteries, CAY 10434 enhanced angiotensin II response as well as 17-ODYA. SC 560 (cyclooxygenase-1-inhibitor) and NS 398 partially blocked the 17-ODYA-effect. In conclusion, 17-ODYA induced endothelial dysfunction by inhibiting CYP-epoxygenase and thus improves vasoconstrictor cyclooxygenase-2 metabolites release acting through TP receptors. The endothelium-independent mechanism of 17-ODYA-effect may involve increase of vasoconstrictor cyclooxygenase-metabolites induced by prostaglandin-ω-hydroxylase-inhibition.

Vascular hyporeactivity to angiotensin II and noradrenaline in a rabbit model of obesity.

This study was conducted to explore the vascular reactivity of angiotensin II and noradrenaline and their relationship with endothelial function in rabbits fed a high-fat diet (HFD). The animals were fed either an HFD or regular chow [control diet (CD)]. After 12 weeks, the rabbits fed the HFD showed higher blood pressure, body weight, and insulin levels. Glucose tolerance was impaired and positively related to blood pressure. An endothelium-independent decrease of the sensitivity to angiotensin II [pD2 endothelium-intact aortic rings (E+) in CD: 8.02 ± 0.07 vs. HFD: 7.60 ± 0.01; pD2 endothelium-removed aortic rings (E-) in CD: 8.16 ± 0.11 vs. HFD: 7.83 ± 0.16] and noradrenaline (pD2 E+ in CD: 6.36 ± 0.06 vs. HFD: 5.29 ± 0.06; pD2 E- in CD: 6.11 ± 0.08 vs. HFD: 5.80 ± 0.08) was found. Noradrenaline desensitized the angiotensin II response (pD2 with noradrenaline pretreatment in E+: 7.03 ± 0.16; in E-: 7.10 ± 0.02), but angiotensin II did not change the noradrenaline response. Acetylcholine maximal relaxation and basal nitric oxide (NO) release were comparable in both diet groups. The efficacy of angiotensin II (Rmax CD: 4604 ± 574 mg vs. HFD: 3251 ± 533 mg) and noradrenaline (Rmax CD: 11,675 ± 804 mg vs. HFD: 7975 ± 960 mg) was reduced in E+. L-N-nitroarginine methyl ester (L-NAME) recovered the efficacy of noradrenaline (Rmax L-NAME: 12,015 ± 317 mg). In contrast, L-NAME had no effect on the angiotensin II response. Noradrenaline enhanced NO levels, but angiotensin II did not. Therefore, NO was associated with hyporeactivity to noradrenaline. The resting potential was more negative in E+, and the endothelium diminished the angiotensin II-induced depolarization. These findings demonstrated that the crosstalk and the endothelium may induce hyporeactivity to angiotensin II and noradrenaline as a mechanism to compensate the increase in the blood pressure in HFD-induced obesity.

Hypercholesterolemia modifies angiotensin II desensitisation and cross talk between alpha(1)-adrenoceptor and angiotensin AT(1) receptor in rabbit aorta.

This study characterised the effect of a hypercholesterolemic diet on the interactions of hormone receptors in the rabbit aorta, both in homologous desensitisation to angiotensin II and cross talk between alpha(1)-adrenoceptors and angiotensin AT(1) receptors. Rabbits were fed either a normal chow or a diet containing 1% cholesterol for 6-7-weeks. Isometric contractions were measured in endothelium-intact or endothelium-removed aortic rings from control and hypercholesterolemic rabbits. Concentration response curves to angiotensin II or noradrenaline incubated with or without prazosin or losartan were performed. In another group, the resting potential was recorded at baseline and following angiotensin II or noradrenaline stimulation. Rabbits fed a hypercholesterolemic diet showed higher plasma levels of total cholesterol and LDL-cholesterol and impaired relaxation to acetylcholine. Homologous desensitisation to angiotensin II was found in endothelium-intact but not in endothelium-removed arteries. Cross talk between alpha(1)-adrenoceptors and angiotensin AT(1) receptors was modified with respect to physiological conditions. In control rabbits, angiotensin II desensitised the noradrenaline response but noradrenaline did not modify the angiotensin II-response. However, in hypercholesterolemic rabbits, angiotensin II sensitised the noradrenaline-response and noradrenaline desensitised the angiotensin II-response. Furthermore, the resting potential remains hyperpolarised after noradrenaline stimulation in hypercholesterolemic rabbits. Modifications in homologous desensitisation to angiotensin II and cross talk between alpha(1)-adrenoceptors and angiotensin AT(1) receptors suggest that hypercholesterolemia induces early tissue dysfunction by altering endothelial and smooth muscle cell regulatory properties. This may be one of the mechanisms by which hypercholesterolemia could be involved in the onset and progression of chronic vascular diseases such as hypertension and arteriosclerosis.

Endothelial dysfunction and improvement of the angiotensin II-reactivity in hypercholesterolemic rabbits: role of cyclooxygenase metabolites.

The aim of this paper was to study the effect of high cholesterol diet on endothelial function and vascular reactivity to angiotensin II and to test the role of vasoconstrictor cyclooxygenase metabolites in this experimental condition. Rabbits were fed with either normal chow or a diet containing 1% cholesterol for 6-7-week. Isometric contractions were measured in rubbed or unrubbed aortic rings. Arteries were contracted with noradrenaline and then exposed to one cumulative dose-response curve to acetylcholine in absence (control) or in presence of indomethacin, (N-[2-cyvlohexyloxy)-4-nitrophenyl]-methanesulfonamide) (NS 398) or 4-hydroxy-2,2,6,6-tetraethylpiperidine-N-oxyl (tempol). After washing the arteries, one cumulative dose-response curve to angiotensin II was constructed in absence or presence of indomethacin, NS 398, [1S-[1 alpha,2 beta (5Z),3 beta,4 alpha]-7-[3-[[2-[(phenylamino) carbonyl]hydrazino]methyl]-7-oxabicyclo[2.2.1] hept-2-yl]-5-heptenoic acid (SQ29548) or 17-octadecynoic acid (17-ODYA). In other group, resting potential was recorded in basal and angiotensin II-stimulated conditions. Indomethacin, NS 398 or 17-ODYA were added to the bath before angiotensin II-stimulation. Rabbits fed on a diet enriched with cholesterol showed higher plasma levels of total cholesterol and LDL. Hypercholesterolemic diet impaired acetylcholine relaxation. Indomethacin normalized endothelium-dependent relaxation whereas NS 398 and tempol had no effect on this phenomenon. Angiotensin II-reactivity was increased in endothelium intact hypercholesterolemic aortic rings and indomethacin, SQ29548 or 17-ODYA blocked this effect. The resting potential of unrubbed hypercholesterolemic arteries was significantly less negative to control after angiotensin II-stimulation. 17-ODYA but not indomethacin prevented angiotensin II-depolarization. High cholesterol diet caused endothelial dysfunction and increased the angiotensin II-reactivity. Both effects were cyclooxygenase1-dependent. Deficit in the NO-production might improve 20-hydroxyeicosatrienoic acid availability, which induces depolarization and angiotensin II-sensitization. In addition, 20-hydroxyeicosatrienoic acid would be metabolized by cyclooxygenase1 to 20-endoperoxides which act through thromboxane A(2)/prostaglandin H(2) receptors contributing to angiotensin II-reactivity increase.

Nitric oxide modulates angiotensin II-induced endothelial vasoconstrictor prostanoid release.

UNLABELLED: This study investigated the modulation of angiotensin II-induced endothelial prostanoid release in rabbit aortic rings. Two cumulative dose response curves with 90-min washing interval were performed. Incubation with L-N(G)-nitroarginine methyl ester (L-NAME) 10(-4) M increased angiotensin II maximal contractile response (E(max)). This effect was reversed by indomethacin 10(-5) M, diphenyliodinum 10(-5) M, Tempol 10(-5) M or ascorbic acid 10(-4) M in both cumulative dose response curves and by SQ 29548 10(-6) M in the second cumulative dose response curve. When segments were treated with tetraethylamonium 10(-3) M but not with glibenclamide 10(-5) M during the washing period, L-NAME recovered its ability to enhance the E(max) in arteries incubated with SQ 29548. CONCLUSIONS: nitric oxide modulates angiotensin II-induced endothelial release of cyclooxygenase-dependent eicosanoids, one of which acts through thromboxane A(2)/prostaglandin H(2) receptors and would decrease K(Ca) channel activity. An increase in free radical production may account for the enhancement of such prostanoid release. Furthermore, it was found that in the present conditions, the release of the hyperpolarizing factor would improve in order to maintain the vascular tone.

Cross talk between angiotensin II and alpha 1 adrenergic receptors in rabbit aorta: role of endothelium.

Interaction between the renin-angiotensin system and the sympathetic nervous system has been proposed to be like a physiological regulation mechanism. The present work was designed to study the cross talk between angiotensin II and adrenergic receptors on the smooth muscle contractile response and the endothelium influence in this phenomenon. Homologous and endothelium independent desensitization of angiotensin II-contractile response was observed. Treatment with noradrenaline between two cumulative doses response curves (CDRC) to angiotensin II caused a rightward shift of the second CDRC in unrubbed arteries and increased the maximal response in rubbed arteries. Prazosin blocked these effects. No homologous desensitization of noradrenaline contractile response was found. Treatment with angiotensin II between two CDRC to noradrenaline caused a loss of affinity in the second CDRC in unrubbed arteries. Losartan was able to avoid this phenomenon. Maximal response was enhanced both in arteries with and without endothelium treated or not with angiotensin II. Results demonstrate homologous and endothelium-independent desensitization of the contractile response to angiotensin II but not to noradrenaline. In addition, heterologous and endothelium-dependent desensitization induced by noradrenaline and angiotensin II on the contractile response to each other was found. Furthermore, results provided the first evidence that there is an endothelium-dependent cross talk between alpha1-adrenergic and angiotensin II receptors in smooth muscle of rabbit aorta.

Role of nitric oxide on the vasorelaxant effect of atrial natriuretic peptide on rabbit aorta basal tone.

The role of nitric oxide (NO) on the vasorelaxant effect of atrial natriuretic peptide (ANP) on the basal tone of rabbit aortic rings conditioned to angiotensin II (Ang II) was studied. ANP aortic relaxation and nitrite release were measured in the presence and absence of endothelium and a NO-synthase inhibitor. Ang II at 10(-8) M triggered a contractile response, conditioning the vessel to a vasorelaxant effect of ANP (10(-8) M). This effect was significantly enhanced by endothelium removal, NG-nitro-L-arginine methyl ester (L-NAME, 10(-4) M), and methylene blue (10(-5) M). ANP decrease of basal tone in Ang-II-sensitized aortic rings was improved when a higher concentration of Ang II was used (l0(-6) M). Basal and Ang-II-stimulated nitrite release were measured in stretched (S) and nonstretched (NS) aortic rings. Nitrite release was significantly increased in S rings (p < 0.001). L-NAME (10(-4) M) partially inhibited nitrite release in both basal and Ang-II-stimulated S aortic rings. In NS aortic rings, the NO inhibitor did not inhibit basal nitrite release but blunted the Ang-II-stimulated nitrite level. A significant negative correlation between nitrite release and the ANP vasorelaxant effect on basal tone was dependent on the Ang-II-sensitizing dose. The present results demonstrate that ANP relaxant effects on aortic basal tone are related to NO levels, which are regulated by S- and Ang-II-concentration-dependent NO generation and quenching.

Efecto de antagonistas de los receptores de angiotensina II y alfa2 adrenérgicos sobre la liberación de óxido nítrico inducida por angiotensina II / Effect of angiotensin II and alpha2 adrenergic receptor antagonists on angiotensin II-stimulated nitric oxide release

El objetivo del presente trabajo fue caracterizar la interacción entre el sistema adrenérgico y la liberación de óxido nítrico (ON) estimulada por angiotensina II en aorta de conejo. Anillos de aorta torácica se colocaron en un baño de órgano aislado. Se equilibró durante 30 min, se lavó y se agregó angiotensina II a diferentes dosis, dejándose actuar 20 min. En otro grupo se efectuaron dos estimulaciones con un intervalo de 60 min. Los antagonistas de angiotensina II: losartan, PD 123319 y Sar1-Leu8-angiotensina II; y el antagonista a2 adrenérgico (yohimbina), todos 10-5 M, y L-NAME o D-NAME 10-2 M, se agregaron antes de estimular con angiotensina II 10-6 M o 5.10-6 M. A otro grupo, además de losartan o PD 123319, se agregó yohimbina. La determinación de nitritos se realizó con el reactivo de Griess. La angiotensina II 10-8 M hasta 10-6 M, incrementó la producción de metabolitos de ON medidos como nitritos con respecto al control. A dosis mayores hubo una disminución con respecto a 10-6 M La liberación de nitritos inducida por angiotensina II cayó en la segunda estimulación con la hormona en todos los casos, mientras el L-NAME la bloqueó. Los antagonistas de angiotensina II la incrementaron sólo a dosis máxima de la hormona, efecto anulado por yohimbina. Asimismo, yohimbina disminuyó la producción de nitritos a dosis de angiotensina II 5.10-6 M pero no 10-6 M. Estos resultados permiten postular que la liberación de ON inducida por angiotensina II sería en parte mediada por estimulación de receptores a2. Los antagonistas de angiotensina II desenmascararían este efecto a dosis máxima de la hormona, mientras que a dosis supramáximas prevalecerían mecanismos inhibitorios que serían compensados por activación a2