Data set on effect of amaranth proteins on the RAS system. In vitro, in vivo and ex vivo assays.

Data set presented in this article is related to the research paper entitled "Effect of amaranth proteins on the RAS system. In vitro, in vivo and ex vivo assays", available in Food Chemistry [1]. In this article, we evaluated the effect on systolic blood pressure of spontaneously hypertensive rats (SHR) of different samples with amaranth proteins/peptides. The effect of these samples on RAS system was evaluated using in vitro and ex vivo assays. The concentration of renin and angiotensin converting enzyme (ACE) was evaluated using two commercial ELISA kits. Renin concentration was estimated through a direct immunoassay and ACE concentration with an immunoassay based on a competitive inhibition. In addition, the ACE inhibitory activity in plasma was evaluated using a spectrophotometric assay according to [2]. Ex vivo experiments were done with thoracic aorta extracted during the surgical procedure employed to obtain blood samples according to [3]. Data presented in this article recollect a very extensive work on how can be affect the RAS system in SHR model using amaranth protein/peptides as potential antihypertensive samples. These data could be useful to design novel functional foods for hypertensive individuals.

Effect of amaranth proteins on the RAS system. In vitro, in vivo and ex vivo assays.

The aim of this work was to analyse the hypotensive effect of amaranth protein/peptides on spontaneously hypertensive rats (SHR). The mechanism of action of these peptides was studied in vivo and ex vivo. We also tested the effect of protection against gastrointestinal digestion (GID) exerted by an O:W emulsion on the integrity of the antihypertensive peptides. All samples tested produced a decrease in blood pressure (SBP). The animals treated with emulsion (GE) and emulsion + peptide (GE+VIKP) showed the most significant reduction in the SBP (42 ±â€¯2 mmHg and 35 ±â€¯2 mmHg, respectively). The results presented suggest that after GID, a variety of peptides with biological activities were released or were resistant to this process. These peptides play a role in the regulation of the SBP by acting on plasma ACE, plasma renin and the vascular system. These results support the use of amaranth protein/peptides in the elaboration of functional foods for hypertensive individuals.

Antioxidant capacity of Maillard reaction products in the digestive tract: An in vitro and in vivo study.

The release of biscuit Maillard reaction products (MRP) with antioxidant capacity was compared by in vitro and in vivo studies. Antioxidant determinations were performed by DPPH, FRAP and ICRED. Results indicated that an intense heat treatment on biscuits increases the amount of MRP with antioxidant capacity (p < 0.05). Besides, a low amount of antioxidant compounds was obtained after enzymatic digestion, whereas the highest proportion was released by colonic bacteria. Moreover, a high amount of non-released antioxidant compounds remained in faeces of Wistar rats; this was only predicted by in vitro ICRED determination. In addition, an increase in the stool amount and in the cecum weight/body weight ratio was observed in animals fed with a diet enriched in MRP (p < 0.05), which indicated a possible prebiotic activity. In conclusion, the in vitro digestion/fermentation procedure combined with ICRED determination would be a useful methodology to predict the release of antioxidant MRP in vivo.

Participation of NO in the vasodilatory action of isoespintanol / Participación de NO en la acción vasodilatadora del isoespintanol

Background: accumulating evidence suggests that natural compounds and specifically monoterpenes exert a vasodilator action. Objetive: to investigate the vascular effects of isoespintanol (2-isopropil-3,6-dimetoxi-5-metilfenol, ISO) monoterpene isolated from the leaves of Oxandra cf xylopioides. Methods: thoracic aortic rings isolated from Wistar rats were contracted with KCl 80 mM and then relaxed by exposure to Ca2+-free solution in absence and in presence of ISO 0.6 mg/mL. The force/tissue ratio (F/W) and the time to obtain 50% of relaxation (T-50) were used to assess the maximal contractile response and the relaxation, respectively. To examine the participation of NO additional experiments were performed under inhibition of nitric oxide synthase with L-NAME (L-NG-Nitroarginine methyl ester). Results: ISO significantly decreased the F/W ratio (257 ± 19 vs. 360 ± 18) and did not change T-50. In presence of L-NAME the effects of ISO on contractile response was abolished. Conclusions: these results demonstrate that ISO exerts a vasodilator effect through NO-dependent pathways and suggest that an inhibition of calcium influx could be the involved mechanism

Antecedentes: la evidencia acumulada sugiere que los compuestos naturales, especialmente monoterpenos, ejercen una acción vasodilatadora. Objetivo: investigar los efectos vasculares del monoterpeno isoespintanol (2-isopropil-3,6-dimetoxi-5-metilfenol, ISO) aislado de hojas de Oxandra cf xylopioides. Métodos: anillos de aorta torácica aislados de ratas Wistar fueron contraídas con cloruro de potasio 80 mM y luego relajadas por exposición a una solución libre de Ca2+ en ausencia y presencia de isoespintanol 0,6 µg/mL. El radio fuerza/tejido (F/T) y el tiempo para obtener 50% de relajación (T50) se usaron para lograr la máxima respuesta contráctil y de relajación, respectivamente. Para evaluar la participación del óxido nítrico, se realizaron experimentos adicionales bajo la inhibición de la óxido nítrico sintetasa con L-NAME (L-NG-éster metílico de nitroarginina). Resultados: Isoespintanol disminuyó el radio F/W significativamente (257 ± 19 vs. 360 ± 18) y no cambió T-50. En presencia de L-NAME, los efectos del isoespintanol en la respuesta contráctil fueron suprimidos. Conclusiones: Estos resultados demuestran que el isoespintanol ejerce un efecto vasodilatador a través de vías NO dependientes y sugiere que la inhibición de la entrada de calcio puede ser el mecanismo involucrado.

Data supporting the cardiac mitochondria calcium handling in female normotensive and spontaneously hypertensive rats.

In association with the published article "Mitochondrial calcium handling in normotensive and spontaneously hypertensive rats: correlation with systolic blood pressure levels" [1], this data article contains information about calcium handling of cardiac mitochondria isolated from female of both rats strains (WKY and SHR). Dataset of mitochondrial permeability transition pore (mPTP) resistance to opening Ca(2+)-mediated, Ca(2+) retention capacity (CRC), time constants and mitochondrial membrane potential (ΔΨm) are showed.

In vivo effects of Maillard reaction products derived from biscuits.

The antioxidant activity, antihypertensive effect and prebiotic activity of Maillard reaction products (MRPs) derived from biscuits were investigated in Wistar rats. Animals were fed the following diets for 6 weeks: control (AIN-93 diet); Asc-diet (AIN-93 diet with ascorbic acid in the drinking water); HT-B diet (containing high amount of MRP derived from biscuits) and LT-B diet (containing negligible amounts of biscuit MRP). Serum antioxidant activity (FRAP, ABTS), as well as lipid peroxidation (TBARS) were determined at the end of the experiment. Results showed that dietary MRP reduced the food efficiency, increased the antioxidant activity of serum, increased the ratio between lactic and total aerobic bacteria, increased water-holding capacity of faeces and reduced blood pressure, but did not reduce mineral absorption. Therefore, the biscuit MRP functional claims could be demonstrated by an in vivo study.

Antithrombotic Effects of Amaranthus hypochondriacus Proteins in Rats.

Cardiovascular disease (CVD) is a major cause of disability and premature death throughout the world. Diets with antithrombotic components offer a convenient and effective way of preventing and reducing CVD incidence. The aim of the present work was to assess in vivo and ex vivo effects of Amaranthus hypochondriacus proteins on platelet plug formation and coagulation cascade. Amaranth proteins were orally administrated to rats (AG, 8 animals) and bleeding time was determined showing no significant difference compared with control rats (CG, 7 animals). However, results show a strong tendency, suggesting that amaranth proteins are involved in the inhibition of thrombus formation. Non-anticoagulated blood extracted from animals was analyzed with the hemostatometer, where AG parameters obtained were twice the values showed by CG. The clotting tests, thrombin time (TT) and activated partial thromboplastin time (APTT), presented a 17 and 14% clotting formation increase respectively when comparing AG with CG. The ex-vivo assays confirm the hypothesis inferring that amaranth proteins are a potential antithrombotic agent.

Effects of the Dietary Addition of Amaranth (Amaranthus mantegazzianus) Protein Isolate on Antioxidant Status, Lipid Profiles and Blood Pressure of Rats.

The effects of the dietary addition of 2.5% (w/w) Amaranthus mantegazzianus protein isolate (AI) on blood pressure, lipid profiles and antioxidative status of Wistar rats were evaluated. Six diets were used to feed animals during 28 days: (base (AIN93G), Chol (cholesterol 1%, w/w), CE (α-tocopherol 0.005%, w/w), CholE (cholesterol 1% (w/w) + α-tocopherol 0.005%, w/w), CAI (AI 2.5% w/w), CholAI (cholesterol 1% (w/w) + AI 2.5%, w/w). Lipid profiles of plasma and liver and faecal cholesterol content were analyzed. Antioxidant status was evaluated by the ferric reducing activity of plasma (FRAP), the 2-thiobarbituric acid (TBA) assay and superoxide dismutase (SOD) activity in plasma and liver. Blood pressure was measured in the tail artery of rats. CholA group presented a significant (α < 0.05) reduction (16%) in the plasma total cholesterol. In liver, the intake of cholesterol (Chol group) induced a significant increment in cholesterol and triglycerides (2.5 and 2.3 times, respectively), which could be decreased (18% and 47%, respectively) by the addition of AI (CholA group). This last group also showed an increased faecal cholesterol excretion (20%). Increment (50%) in FRAP values, diminution of TBA value in plasma and liver (70% and 38%, respectively) and diminution of SOD activity (20%) in plasma of CholA group suggest an antioxidant effect because of the intake of AI. In addition, CA and CholA groups presented a diminution (18%) of blood pressure after 28 days.

Mitochondrial calcium handling in normotensive and spontaneously hypertensive rats: correlation with systolic blood pressure levels.

The aim was to study the mitochondrial Ca(2+) handling of mitochondria isolated from normotensive Wistar Kyoto (WKY) and spontaneously hypertensive rats (SHR) hearts and to establish a possible correlation with systolic blood pressure (SBP). Mitochondrial swelling after Ca(2+) addition, Ca(2+)-retention capacity (CRC) by calcium green method, and membrane potential (ΔΨm) were assessed. SBP was 124±1 (WKY) and 235±6mmHg (SHR). CRC, Ca(2+) response and ΔΨm were lower in SHR than WKY mitochondria. The conclusion is: the more depolarized state of SHR than WKY mitochondria results in an abnormal Ca(2+) handling and this event is closely associated with the SBP.

CaMKII-dependent phosphorylation of cardiac ryanodine receptors regulates cell death in cardiac ischemia/reperfusion injury.

Ca(2+)-calmodulin kinase II (CaMKII) activation is deleterious in cardiac ischemia/reperfusion (I/R). Moreover, inhibition of CaMKII-dependent phosphorylations at the sarcoplasmic reticulum (SR) prevents CaMKII-induced I/R damage. However, the downstream targets of CaMKII at the SR level, responsible for this detrimental effect, remain unclear. In the present study we aimed to dissect the role of the two main substrates of CaMKII at the SR level, phospholamban (PLN) and ryanodine receptors (RyR2), in CaMKII-dependent I/R injury. In mouse hearts subjected to global I/R (45/120min), phosphorylation of the primary CaMKII sites, S2814 on cardiac RyR2 and of T17 on PLN, significantly increased at the onset of reperfusion whereas PKA-dependent phosphorylation of RyR2 and PLN did not change. Similar results were obtained in vivo, in mice subjected to regional myocardial I/R (1/24h). Knock-in mice with an inactivated serine 2814 phosphorylation site on RyR2 (S2814A) significantly improved post-ischemic mechanical recovery, reduced infarct size and decreased apoptosis. Conversely, knock-in mice, in which CaMKII site of RyR2 is constitutively activated (S2814D), significantly increased infarct size and exacerbated apoptosis. In S2814A and S2814D mice subjected to regional myocardial ischemia, infarct size was also decreased and increased respectively. Transgenic mice with double-mutant non-phosphorylatable PLN (S16A/T17A) in the PLN knockout background (PLNDM) also showed significantly increased post-ischemic cardiac damage. This effect cannot be attributed to PKA-dependent PLN phosphorylation and was not due to the enhanced L-type Ca(2+) current, present in these mice. Our results reveal a major role for the phosphorylation of S2814 site on RyR2 in CaMKII-dependent I/R cardiac damage. In contrast, they showed that CaMKII-dependent increase in PLN phosphorylation during reperfusion opposes rather than contributes to I/R damage.

Increased Na⁺/Ca²âº exchanger expression/activity constitutes a point of inflection in the progression to heart failure of hypertensive rats.

UNLABELLED: Spontaneously hypertensive rat (SHR) constitutes a genetic model widely used to study the natural evolution of hypertensive heart disease. Ca²âº-handling alterations are known to occur in SHR. However, the putative modifications of Ca²âº-handling proteins during the progression to heart failure (HF) are not well established. Moreover, the role of apoptosis in SHR is controversial. We investigated intracellular Ca²âº, Ca²âº-handling proteins and apoptosis in SHR vs. control Wistar rats (W) from 3 to 15 months (mo). Changes associated with the transition to HF (i.e. lung edema and decrease in midwall fractional shortening), occurred at 15 mo in 38% of SHR (SHRF). In SHRF, twitch and caffeine-induced Ca²âº transients, significantly decreased relative to 6/9 mo and 15 mo without HF signs. This decrease occurred in association with a decrease in the time constant of caffeine-Ca²âº transient decay and an increase in Na⁺/Ca²âº exchanger (NCX) abundance (p<0.05) with no changes in SERCA2a expression/activity. An increased Ca²âº-calmodulin-kinase II activity, associated with an enhancement of apoptosis (TUNEL and Bax/Bcl2) was observed in SHR relative to W from 3 to 15 mo. CONCLUSIONS: 1. Apoptosis is an early and persistent event that may contribute to hypertrophic remodeling but would not participate in the contractile impairment of SHRF. 2. The increase in NCX expression/activity, associated with an increase in Ca²âº efflux from the cell, constitutes a primary alteration of Ca²âº-handling proteins in the evolution to HF. 3. No changes in SERCA2a expression/activity are observed when HF signs become evident.

Myocardial alterations in the murine model of fabry disease can be reversed by enzyme replacement therapy.

BACKGROUND: Fabry disease results from deficiency of alpha-galactosidase A (AGA), causing lysosomal storage of globotriaosylceramide in heart and other tissues. Since 2003, enzymatic replacement therapy with recombinant AGA agalsidase alfa (R-AGA) was approved for clinical use. METHODS: We evaluated whether, in mice knocked out for AGA (FM, n = 31), the myocardium was altered with respect to the wild-type mice (WT, n = 25) and whether alterations were reversed in FM treated with intravenous R-AGA, 0.5 mg/kg every other week during 2 months (FM-AGA, n = 12). RESULTS: Left ventricular (LV) contractility was depressed in FM, evaluated by LV ΔP/Δt (FM = 2832 ± 85 mm Hg/s, WT = 3179 ± 119 mm Hg/s; P < 0.05), papillary muscle contraction (FM = 39.8 ± 17.3 mg, WT = 67.5 ± 15.7 mg; P < 0.05), or shortening fraction measured by M-mode echocardiography (FM = 30% ± 6%, WT = 47% ± 2%; P < 0.05). LV stiffness (arrested hearts) decreased in FM (FM = 35.57 ± 3.5 mm Hg/20 µl; WT = 68.86 ± 6.12 mm Hg/20 µl; P < 0.05). FM myocytes showed augmented size, disorganized architecture, and intracytoplasmic vacuolization. Alterations reverted in FM-AGA: LV ΔP/Δt = 3281 ± 456 mm Hg/s and LV stiffness = 58.83 ± 2.15 mm Hg/20 µl, with normalization of myocyte architecture. No reversion was detected with AGA solvent. CONCLUSIONS: The FM represent a mild, early stage of the disease, since myocardial alterations are not prominent and appear in nonhypertrophic hearts. Reversion of alterations in the FM-AGA suggests that enzymatic replacement therapy can be useful when administered in early stages of this disease.

Influence of nitric oxide-mediated vasodilation on the blood pressure measured with the tail-cuff method in the rat.

Systolic blood pressure (SBP) is frequently measured in rats by the tail cuff method, which usually comprises pulse/flow disappearance and reappearance during cuff inflation (Inf) and deflation (Def), separated by an interval between cycles (IBC). Although Def values are habitually used to estimate SBP, in 58 Wistar rats we found (Def-Inf) to be -6 +/- 1 mmHg, indicating that Def < Inf in most cases. When the IBC was lengthened to 2 min, (Def-Inf) was increased to -17 +/- 2 mmHg, indicating the probable accumulation of a vasodilating metabolite. This increase of (Def-Inf) was prevented by papaverine, indicating its relation to smooth muscle contractility. Adrenergic blockade did not prevent the increase of (Def-Inf), but pretreatment with L-NAME decreased it to -5 +/- 2 mmHg (p < 0.05). Simultaneous measurement of SBP by tail-cuff method and carotid cannulation revealed that the Inf value was the most accurate estimation of intravascular SBP. We conclude that: (1) the Inf value should be taken as representative of SBP, since depending on the duration of suprasystolic compression the Def value can underestimate it, and (2) nitric oxide accumulation due to flow deprivation was the main cause of SBP underestimation by Def values.

Aspectos estructurales y funcionales de la vena safena humana utilizada como puente aorto-coronario en la cirugia de revascularización miocárdica / Structural and functional aspects of the human saphenous vein used as aorto-coronary graft in myocardial revascularization

La vena safena humana (VSH) se utiliza como puente en la cirugía de revascularización coronaria y de otros lechos arteriales, especialmente de miembros inferiores. Dado que los puentes de VSH presentan un porcentaje considerable de obliteración, numerosos estudios han investigado los factores que promoverían la producción de la estenosis en los mismos. Este artículo describe resultados sobre las condiciones estructurales y funcionales que confluyen para producir la obstrucción de los puentes de VSH. Se analiza la reactividad de la VSH a agonistas fisiológicos, incluídos los factores contrayentes y relajantes derivados del endotelio, por su importancia en determinar el vasoespasmo y en modificar la expresión de factores de crecimiento tisular y/o promotores de procesos trombóticos y ateromatosos. Se describen mecanismos involucrados en la regulación del estado contráctil de los miocitos lisos, en particular la actividad de canales de K+ de la membrana

Vasodilatadores en arterias radiales humanas aisladas / Vasodilators in isolated human radial arteries

Este trabajo se diseñó para evaluar la efectividad de diversos vasodilatadores aplicados tópicamente para prevenir la hiperreactividad de las arterias radiales (AR) implantadas como bypass aortocoronario. De cada uno de los remanentes de AR provenientes de 20 pacientes operados se obtuvieron 4 anillos que se incubaron por 30 minutos en condiciones control (n = 20) o en presencia de 30 µM de diltiazem (DILT, n = 6), mibefradil (MIBE, n = 4) o mezcla de verapamil + nitroglicerina (VP-NTG, n = 6). La subsiguiente exposición a CIK 80 mM (en ausencia de vasodilatadores) provocó una contracción sostenida en los anillos control, que fue atenuada en un 35 ñ 9 por ciento por DILT, 48 ñ 13 por ciento por VP-NTG y 69 ñ 20 por ciento por MIBE (p < 0.05). La preincubación con vasodilatadores provocó también la disminución de frecuencia e intensidad de contracciones rítmicas espontáneas de la AR. En anillos almacenados en frío por 24 hs y luego reestimulados con CIK 80 mM el efecto depresor fue aun evidente: DILT 53 ñ 6 por ciento, VP-NTG 46 ñ 14 por ciento y MIBE 61 ñ 9 por ciento (p < 0.05). El efecto del MIBE fue más intenso y persistente que el de DILT o VP-NTG, aún a concentraciones que provocan un igual efecto depresor inicial. Se concluye que la exposición a vasodilatadores durante un período equivalente a la duración de la preparación de la AR a implantar produce una atenuación de la reactividad arterial que proporcionaría una protección adicional contra el espasmo durante el postoperatorio inmediato.

Insulina, reatividad valcular me hipertension arterial / Insulin, vascular reactiviry and hypertension

Varios estudios epidemiológicos indican que hay una relación entre hiper-insulinemia, resistencia insulínica e hipertensión arterial. La insulina estimula el sistema nervioso simpático, produce retención renal de Na+ y modifica en forma directa mecanismos vasculares (contrayentes y relajantes); estos efectos pueden justificar que la insulina aumente o disminuya la presión arterial. la ausencia de los efectos vasodilatadores debido a resistencia insulínica y/o la mayor manifestación de los efectos hipertensores en caso de hiperinsulinemia podrían ser el nexo entre la insulina y la hipertensión arterial.

Efectos de la insulina sobre la respuesta contractil y la captacion de calcio en aorta de rata / Effect of insulin on contractile response and calcium captation in rat aorta

La insulina afecta mecanismos fisiológicos generales que regulan la presión arterial, y a nivel celular modifica las funciones del endotelio y del mosculo liso vascular, que son determinantes de la resistencia periférica. Describimos los efectos de la preincubación con insulina (40 muU/ml, durante 1-2 hs) sobre la reactividad contráctil de anillos intactos de aorta de rata y sobre la captaci>n de 45Ca2+ en segmentos de aorta de rata hipermeabilizados por tratamiento con EGTA. La preincubación con insulina no afectó las contracciones inducids por 1 muM de NA, ni la relajación de las mismas inducida por 10 mM de cafeína. La respuesta contractil a 1 muM de Ang-II (que en la aorta de rata es independiente de endotelio) fue estimulada por la preincubación con insulina en la fuerza máxima desarrollada y en la velocidad de relajación espontánea de la contracción. La diferencia en la captación de 45Ca2+ en RS entre los segmentos de aorta tratados y no tratados con insulina fue mayor a los 5 minutos con respecto a la medida a los 30 minutos. Se concluye que la preincubación con insulina afecta en forma directa la respuesta mecánica del mosculo liso aórtico estimulado con Ang-II y se propone a la modificación de la actividad del RS como uno de los mecanismos mediante el cual la insulina participa en la regulación del Ca2+ citosólico.

Depositos de calcio sensibles a la noradrenalina en arterias de la cola de ratas normotensas y espontaneamente hipertensas: efectos de la rianodina y cafeina / Norepinephrine sensitive calcium pools in tail arteries of normotensiol and spontaneous hypertensive rats: effects of ryanodine and caffeine

Se estudiaron los efectos de la Rianodina (RI) y cafeína (CF) sobre las contracciones inducidas por noradrenalina (NA) en arterias de la cola de ratas espontáneamente hipertensas (SHR) y normotensas (WKY). El depósito intracellular de calcio sensible a NA fue vaciado completamente por exposición a NA 1 µM en solución libre de calcio, y fue responsable de un 40% de la contracción a NA en presencia de calcio 1.6 mM. Sin embargo, solamente en 60% del depósito fue utilizado para la contracción en calcio 1.6 mM. La reexposición al calcio extracelular rellenó el depósito sensible a NA en menos de 10 minutos, pero mientras el depóstio de la WKY captó aproximadamente el mismo calcio que tenía previamente (a juzgar por la magnitud de la respuesta mecánica posterior en solución libre de calcio), la SHR captó aproximadamente el doble de calcio en las msmas condiciones. La RI impidió el relleno del depósito en la SHR y WKY, sin liberar calcio del depósito y sin afectar el influjo de calcio a través de la membrana. La CF también previno el relleno de los depósitos sensibles a NA, pero también liberó calcio del depósito y promovió el ingreso de calcio a través de la membrana celular. Se concluye que la principal acción de la RI em el músculo liso de la cola de la rata es prevenir la captación de calcio por el depósito intracelular sensible a NA, mientras que la CF tiene varios efectos: inhibición de la captación de calcio por el depósito, liberación de calcio por depóstio, y apertura de canales de calcio de la membrana celular. Además, en la SHR (pero no en la WKY) la pérdida de calcio de la membrana vuelve a ésta más permeable al calcio, permitiendo una captación aumentada de calcio por el depósito intracelular en una subsiguiente exposición al calcio extracelular

Influence of norepinephrine-sensitive intracellular calcium stores on the relaxant response to diltiazem in rat aorta

La respuesta contráctil a la noradrenalina (NA) en la aorta de rata tiene un componente rápido inicial, atribuido a la liberación de calcio intracelular, y uno lento provocado por el subsiguiente influjo de calcio. La acción relajante del bloqueante de la entrada de calcio Diltiazem (DZ) 10 µM fue ensayada frente a diferentes tipos de respuesta a la NA 1 µM: a) Una respuesta a 1a NA en Ca= 1.35 mM, en la cual se producen ambos componentes rápido y lento, fue la disminuida en un 36 ñ 4%; b) mediante incubación previa con Prazosin 0.01µM se eliminó el componente rápido, apareciendo solamente el lento, con una magnitud similar a la respuesta obtenida en (a). Esta contracción fue atenuada en un 47 ñ 3%; c) el depósito intracelular de calcio fue vaciado por exposición a NA en una solución libre de calcio y con EGTA 2 mM. La exposición subsiguiente a CA= 1.35 mM provocó solamente un componente lento, el cual fue deprimido por DZ en un 61 ñ 4%. Como los protocolos precedentes sugierem un efecto relajante creciente del DZ a medida que el depósito intracelular de calcio se encuentra más vacío, se observó su efecto en una situación intermedia. El depósito fue vaciado como en (c) y luego rellenado por exposición breve a Ca=1.35mM. En este caso el DZ disminuyó la contracción 51 ñ 3% (20 segundos de relleno) y 41 ñ 3% (60 segundos de relleno). Se obtuvieron resultados similares con DZ o.1, 1 y 100 µM. Se concluye que la acción relajante del DZ sobre la contracción por NA en aorta de rata es inversamente proporcional a la cantidad de calcio intracelular que participa en dicha contracción