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1. The vasodilator action of angiotensin (Ang) II has not yet been demonstrated in spontaneously hypertensive rats (SHR), nor have any possible changes in this response during the development of hypertension. 2. In the present study, the vasodilator effect of AngII was evaluated in the rat isolated, preconstricted mesenteric arterial bed (MAB) from 6- (young) and 24-week-old (adult) SHR and compared with effects on MAB from age-matched normotensive rats (control). 3. Angiotensin II (10–300 nmol) induced vasodilation in noradrenaline (NA)-preconstricted MAB that was greater in vessels from young compared with adult rats in both the control and SHR groups. Angiotensin II-induced vasodilation was reduced by the angiotensin AT2 receptor antagonist PD 123319 (10 µmol/L), the angiotensin-(1–7) receptor antagonist A779 (1 µmol/L) and the bradykinin B2 receptor antagonist HOE-140 (0.01 µmol/L), but not by the AT1 receptor antagonist losartan (30 µmol/L). Expression of AT2 receptors was weak in vessels from adult control rats compared with that in young control rats, whereas in young SHR AT2 receptor expression was increased compared with that in young control rats. This increased expression of AT2 receptors was maintained in adult SHR and there was no significant difference in AT2 receptor expression between young and old SHR. 4. The findings of the present suggest that AngII induces an AT2 receptor-mediated vasodilator effect in the MAB via activation of angiotensin-(1–7) and bradykinin receptors, an action that is reduced in adult control rats and adult SHR. In adult control rats, the attenuated response of AngII is probably due to endothelial dysfunction and reduced expression of AT2 receptors, whereas in adult SHR it is associated with endothelial dysfunction alone. Increased expression of AT2 receptors in SHR may represent a counteracting response for modulating blood pressure. [ABSTRACT FROM AUTHOR]

1. The mechanisms involved in the vasodilator actions of angiotensin II (Ang II) have not yet been completely elucidated. We investigated the potential mechanisms that seem to be involved in the Ang II vasodilator effect using rat isolated mesenteric vascular bed (MVB). 2. Under basal conditions, Ang II does not affect the perfusion pressure of MVB. However, in vessels precontracted with norepinephrine, Ang II induces vasodilation followed by vasoconstriction. Vasoconstrictor, but not the vasodilation of Ang II, is inhibited by AT(1) antagonist (losartan). The vasodilator effect of Ang II was not inhibited by AT(2), angiotensin IV and angiotensin 1-7 receptor antagonists alone (PD 123319, divalinal, A 779, respectively). 3. The vasodilator effect of Ang II is significantly reduced by endothelial removal (deoxycholic acid), but not by indomethacin. Inhibition of NO-synthase by N(G)-nitro-l-arginine methyl ester (l-NAME) and guanylyl cyclase by 1H-[1,2,3] oxadiazolo [4,4-a] quinoxalin-1-one (ODQ) reduces the vasodilator effect of Ang II. This effect is also reduced by tetraethylammonium (TEA) or l-NAME, and a combination of l-NAME plus TEA increases the inhibitory effect of the antagonists alone. However, indomethacin does not change the residual vasodilator effect observed in vessels pretreated with l-NAME plus TEA. 4. In vessels precontracted with norepinephrine and depolarized with KCl 25 mm or treated with Ca(2+)-dependent K(+) channel blockers (charybdotoxin plus apamin), the effect of Ang II was significantly reduced. However, this effect is not affected by ATP and voltage-dependent K(+) channel blockers (glybenclamide and 4-aminopyridine). 5. Inhibition of kininase II with captopril significantly potentiates the vasodilator effect of bradykinin (BK) and Ang II in the rat MVB. The inhibitory effect of the B(2) receptor antagonist HOE 140 on the vasodilator effect of Ang II is further enhanced by PD 123319 and/or A 779. 6. The present findings suggest that BK plays an important role in the endothelium-dependent vasodilator effect of Ang II. Probably, the link between Ang II and BK release is modulated by receptors that bind PD 123319 and A 779. [ABSTRACT FROM AUTHOR]

The inactivation of bradykinin on passage across the human foetal placental circulation was investigated in six full-term human placentas. The placentas were perfused with a modified Krebs-Henseleit solution and placenta perfusion pressure was recorded. Samples collected at the arterial inflow and at the venous effluent were assayed on the isolated guinea-pig ileum as an estimation of bradykinin activity. Bradykinin (100 ng ml-1) was infused through the foetal placental vessels before and during captopril 4 X 10(-7) M. Bradykinin produced a transient increase in placental vascular resistance that was not potentiated by captopril. Bradykinin activity was completely abolished after passage through the foetal placental circulation, and the inactivation was blocked by captopril. These data suggest that angiotensin I converting enzyme (kininase II) might occur in the foetal placental vessels. [ABSTRACT FROM AUTHOR]

1. Nitric oxide (NO) produced by human platelets plays an important role in all stages of platelet activation.l-Arginine, the precursor for NO synthesis, modulates NO production by platelets. Thel-arginine analogues asymmetric dimethylarginine (ADMA) andNG-monomethyl-l-arginine (l-NMMA) are endogenous inhibitors of nitric oxide synthase (NOS), involved in the physiopathology of arterial hypertension. The aim of the present study was to investigate the inhibitory effects of endogenous and exogenousl-arginine analogues onl-arginine influx in platelets from healthy controls and hypertensive patients.2. Twelve patients with uncomplicated essential hypertension (stage I) and 15 age-matched normotensive controls participated in the present study. Platelets were isolated and incubated withl-[3H]-arginine and increasing concentrations ofl-arginine analogues (5–2000 µmol/L).3. The influx ofl-arginine was inhibited in a concentration-dependent manner byl-NMMA in platelets from controls (Ki = 42 ± 6 µmol/L) and this inhibitory effect was markedly higher in hypertensive platelets (Ki = 23 ± 4 µmol/L).4. Similarly, the Ki for ADMA inhibition ofl-arginine transport was significantly more pronounced in platelets from hypertensive patients (Ki = 16 ± 1 µmol/L) compared with controls (Ki = 27 ± 2 µmol/L).5. In contrast,NG-nitro-l-arginine methyl ester (l-NAME) was found to be a weak inhibitor ofl-arginine influx in platelets from controls (Ki = 1917 ± 319 µmol/L) and hypertensive patients (Ki = 2279 ± 578 µmol/L). Aminoguanidine, a selective inhibitor of inducible NOS, failed to inhibitl-arginine transport.6. Our findings provide the first evidence that ADMA andl-NMMA markedly inhibitl-arginine transport in human platelets, an effect that is more pronounced in hypertensive patients. It is possible that endogenousl-arginine analogues, by inhibiting NO synthesis, are involved in the platelet activation present in hypertension. [ABSTRACT FROM AUTHOR]

Objectives: Alterations in cardiovascular and skeletal muscle function are hallmarks of ageing that lead to exercise intolerance. We aimed to examine whether the treatment with Euterpe oleracea Mart. seed extract (ASE) associated with exercise training improves aerobic exercise performance by promoting healthy ageing in the elderly., Methods: Male Wistar rats were divided into five groups: Young (3 months), Old (18 months), Old+ASE (ASE 200 mg/kg/day), Old+Training (exercise training 30 min/day; 5 days/week) and Old+Training+ASE, for 4 weeks., Key Findings: ASE treatment increased the exercise time and the running distance concerning the initial maximal treadmill stress test (MTST) in the Old+Training+ASE group. Exercise training or ASE treatment restored the aorta oxidative damage and antioxidant defence. It reduced the acetylcholine (ACh)-induced vasodilation in the aorta of old animals to the same values as the young and improved hypertension. Only the association of both strategies restored the ACh-induced vasodilation in mesentery arteries. Remarkably, exercise training associated with ASE increased the antioxidant defence, nitrite levels and expression of the mitochondrial SIRT-1, PGC1α in soleus muscle homogenates., Conclusions: ASE treatment associated with exercise training contributes to better exercise performance and tolerance in ageing by improving vascular function, oxidative stress and activating the muscle SIRT-1/PGC-1α pathway., (© The Author(s) 2023. Published by Oxford University Press on behalf of the Royal Pharmaceutical Society. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Abstract: This study aimed to determine if açai seed extract (ASE) could reverse pre-existing cardiovascular and renal injury in an experimental model of renovascular hypertension (2 kidney, 1 clip, 2K1C). Young male rats (Wistar) were used to obtain 2K1C and sham groups. Animals received the vehicle, ASE (200 mg/kg/d), or enalapril (30 mg/kg/d) in drinking water from the third to sixth week after surgery. We evaluated systolic blood pressure by tail plethysmography, vascular reactivity in the rat isolated mesenteric arterial bed (MAB), serum and urinary parameters, plasma inflammatory cytokines by ELISA, MAB expression of endothelial nitric oxide synthase and its active form peNOS by Western blot, plasma and MAB oxidative damage and antioxidant activity by spectrophotometry, and vascular and cardiac structural changes by histological analysis. ASE and enalapril reduced the systolic blood pressure, restored the endothelial and renal functions, and decreased the inflammatory cytokines and the oxidative stress in 2K1C rats. Furthermore, both treatments reduced vascular and cardiac remodeling. ASE substantially reduced cardiovascular remodeling and recovered endothelial dysfunction in 2K1C rats probably through its antihypertensive, antioxidant, and anti-inflammatory actions, supplying a natural resource for the treatment of renovascular hypertension., Competing Interests: The authors report no conflicts of interest., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Many studies suggest a protective role of phenolic compounds in mood disorders. We aimed to assess the effect of Euterpe oleracea (açaí) seed extract (ASE) on anxiety induced by periodic maternal separation (PMS) in adult male rats. Animals were divided into 6 groups: control, ASE, fluoxetine (FLU), PMS, PMS+ASE, and PMS+FLU. For PMS, pups were separated daily from the dam for 3 h between postnatal day (PN) 2 and PN21. ASE (200 mg·kg -1 ·day -1 ) and FLU (10 mg·kg -1 ·day -1 ) were administered by gavage for 34 days after stress induction, starting at PN76. At PN106 and PN108, the rats were submitted to open field (OF) and forced swim tests, respectively. At PN110, the rats were sacrificed by decapitation. ASE increased time spent in the center area in the OF test, glucocorticoid receptors in the hypothalamus, tropomyosin receptor kinase B (TRKB) levels in the hippocampus, and nitrite levels and antioxidant activity in the brain stem (PMS+ASE group compared with PMS group). ASE also reduced plasma corticotropin-releasing hormone levels, adrenal norepinephrine levels, and oxidative damage in the brain stem in adult male offspring submitted to PMS. In conclusion, ASE treatment has an anti-anxiety effect in rats submitted to PMS by reducing hypothalamic-pituitary-adrenal axis reactivity and increasing the nitric oxide (NO)-brain-derived neurotrophic factor (BDNF)-TRKB pathway and antioxidant defense in the central nervous system. Novelty ASE has anti-anxiety and antioxidant effects in early-life stress. ASE reduces hypothalamic-pituitary-adrenal axis reactivity. The anxiolytic effect of ASE may involve activation of the NO-BDNF-TRKB pathway in the central nervous system.

This study investigated the therapeutic potential of Euterpe oleracea extract (açaí) on the growth and survival of endometriotic lesions using an experimental model. Twenty female Sprague-Dawley rats were randomized into two groups after the implantation and establishment of autologous endometrium onto the peritoneum abdominal wall and treated with 200 mg/kg hydroalcoholic solution extract from açaí stone or vehicle via gastric tube for 30 consecutive days. Body weight, lesion surface areas, histological and immunohistochemistry analyses of vascular endothelial growth factor (VEGF), VEGF receptor-2 (VEGFR-2), metalloproteinase-9 (MMP-9), cyclooxygenase-2 (COX-2) and F4-80 were performed. Levels of VEGF, VEGFR-2, MMP-9 and COX-2 mRNA were measured. Flow cytometry of F4-80 was performed, and ELISA immunoassays measured prostaglandin E2 (PGE2), VEGF and nitric oxide (NO) and concentrations. Macrophage cell line J774.G8 was treated with 10, 20, and 40 μg/mL of açaí for 24, 48 and 72 h, and cell viability was measured using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays. Açaí treatment significantly decreased the implant size, and histological examination indicated atrophy and regression. A reduction in immunostaining and mRNA expression of VEGF, MMP-9 and COX-2 was observed, and F4-80 was lower in the treated group than the control group. The treated group also exhibited lower concentrations of PGE2, VEGF and NO compared to the control group. Macrophages cells treated with 20 and 40 μg/ml of açaí reduced cell viability in about 50% after 24, 48 and 72 h. Our results suggest that açaí effectively suppressed the establishment and growth of endometriotic lesions, and this agent is a promising novel pharmacological therapeutic treatment for endometriosis., Competing Interests: The authors have declared that no competing interests exist.

This study investigated the endothelium-dependent vasorelaxant effects of the essential oil of Ocimum gratissimum (EOOG) in aortas and mesenteric vascular beds isolated from rats. EOOG (3-300 µg/mL) relaxed the tonic contractions induced by phenylephrine (0.1 µmol/L) in isolated aortas in a concentration-dependent manner in both endothelium-containing and endothelium-denuded preparations. This effect was partially reversed by L-NAME (100 µmol/L) but not by indomethacin (10 µmol/L) or TEA (5 mmol/L). In mesenteric vascular beds, bolus injections of EOOG (30, 50, 100, and 300 ng) decreased the perfusion pressure induced by noradrenaline (6 µmol/L) in endothelium-intact preparations but not in those treated with deoxycholate. L-NAME (300 µmol/L) but not TEA (1 mmol/L) or indomethacin (3 µmol/L) significantly reduced the vasodilatory response to EOOG at all of the doses tested. Our data showed that EOOG exerts a dose-dependent vasodilatory response in the resistance blood vessels of rat mesenteric vascular beds and in the capacitance blood vessel, the rat aorta. This action is completely dependent on endothelial nitric oxide (NO) release in the mesenteric vascular beds but only partially dependent on NO in the aorta. These novel effects of EOOG highlight interesting differences between resistance and capacitance blood vessels.

Objectives: This study examined the effect of Vitis vinifera grape skin extract (ACH09) on hyperglycaemia and the insulin-signalling cascade in alloxan-treated mice., Methods: Glycaemia, serum insulin and Western blot analysis of insulin cascade proteins were evaluated in the gastrocnemius muscles of four groups of adult mice: control, ACH09 (200 mg/kg per day, p.o.), alloxan (300 mg/kg, i.p.) and alloxan + ACH09. Insulin secretion in isolated pancreatic islets was also studied., Key Findings: Glycaemia values in the alloxan + ACH09 and ACH09 groups were significantly lower than in the alloxan-treated and control groups, respectively. Increased insulin resistance (HOMA index) was observed in the alloxan-treated group but not in the alloxan + ACH09 group. Insulin receptor content and Akt phosphorylation were significantly greater in the alloxan + ACH09 group compared with the alloxan-treated group. The glucose transporter (GLUT-4) content was reduced in alloxan-treated mice compared with the control group, while alloxan + ACH09 and ACH09-treated mice showed a significant increase in GLUT-4 content. ACH09 treatment did not change glucose-induced insulin secretion in isolated pancreatic islets., Conclusions: The results suggest that ACH09 has hypoglycaemic and antihyperglycaemic effects that are independent of an increase in insulin release but are probably dependent on an increase in insulin sensitivity resulting from an activation of the insulin-signalling cascade in skeletal muscle., (© 2011 The Authors. JPP © 2011 Royal Pharmaceutical Society.)

Background/aims: Drinking red wine is associated with a decreased mortality from coronary heart diseases. This study examined whether polyphenols contained in a grape skin extract (GSE) triggered the endothelial formation of nitric oxide (NO) and investigated the underlying mechanism., Methods: Vascular reactivity was assessed in organ chambers using porcine coronary artery rings in the presence of indomethacin (a cyclooxygenase inhibitor) and charybdotoxin plus apamin (inhibitors of endothelium-derived hyperpolarizing factor-mediated responses). The phosphorylation level of Src, Akt and endothelial NO synthase (eNOS) were assessed by Western blot analysis, and the formation of reactive oxygen species (ROS) was investigated using dihydroethidine and dichlorodihydrofluorescein., Results: GSE-induced endothelium-dependent relaxations were abolished by N(G)-nitro-L-arginine (an eNOS inhibitor) and ODQ (a soluble guanylyl cyclase inhibitor), and they were reduced by MnTMPyP, polyethyleneglycol catalase, PP2 (an inhibitor of Src kinase) and wortmannin (an inhibitor of phosphoinositide 3-kinase). GSE caused phosphorylation of Src, which was prevented by MnTMPyP. It also caused phosphorylation of Akt and eNOS, which were prevented by MnTMPyP, polyethyleneglycol catalase, PP2, wortmannin and LY294002. GSE elicited the formation of ROS in native and cultured endothelial cells, which was prevented by MnTMPyP., Conclusions: GSE causes endothelium-dependent NO-mediated relaxations of coronary arteries. This effect involves the intracellular formation of ROS in endothelial cells leading to the Src kinase/phosphoinositide 3-kinase/Akt-dependent phosphorylation of eNOS.

Objective: To investigate the effects of sildenafil on noradrenaline- and potassium-induced contractions of isolated human seminal vesicles (SVs), as premature ejaculation is a relatively common male sexual dysfunction that currently lacks an adequate therapy, and recent in vitro tests showed that sildenafil induces relaxation of rodent isolated SVs, but it is not known whether it also inhibits isolated human SV., Material and Methods: Isolated strips of human SVs were suspended in an organ bath and cumulative concentration-response curves to either noradrenaline or KCl were constructed in the presence and absence of sildenafil to evaluate its inhibitory actions., Results: Sildenafil (25-100 microm) induced concentration-dependent inhibitory effects on the human SV contracted by either noradrenaline or KCl. These actions of sildenafil do not therefore appear to be mediated via a competitive antagonism of alpha-adrenoceptors and are consistent with its recognized ability to inhibit phosphodiesterase-5., Conclusions: The present results show an important inhibitory action of sildenafil in the isolated human SV, supporting the therapeutic indication of this drug for treating premature ejaculation.

An alcohol-free grape-skin extract (GSE) obtained from skins of Vitis labrusca has significant anti-hypertensive, antioxidant and vasodilator effects. According to our previous results, the vasodilator effect of GSE in the isolated mesenteric vascular bed (MVB) of the rat is dependent on endothelium and partially dependent on nitric oxide (NO). In the MVB of the rat pre-contracted with norepinephrine (NE), bolus injections of GSE induced a long-lasting dose-dependent vasodilation that is significantly reduced after the treatment with 1H-[1,2,3] oxadiazolo [4,4-a] quinoxalin-1-one (ODQ). Additionally, in vessels pre-contracted with norepinephrine and depolarized with KCl (25 mM) or treated with Ca(2+)-dependent K(+)-channel blockers charybdotoxin (ChTx) plus apamin, the vasodilator effect of GSE was significantly reduced and almost abolished by ChTx plus apamin plus L-NAME. However, the vasodilator effect of GSE was unaffected by D-Arg[Hyp(3),Thi(5),D-Tic(7),Oic(8)]bradykinin (HOE-140), atropine, yohimbine, pyrilamine and 4-aminopyridine (4-AP). The vasoconstriction response elicited by bolus injection of KCl was not affected by GSE, whereas the vasoconstrictor response induced by NE was dose-dependently and completed inhibited by GSE in the presence but not in the absence of endothelium. However, NE-induced vasoconstriction in calcium-free condition or without endothelium was not reduced by GSE. The present results demonstrate that GSE induces a vasodilator effect in the rat MVB, which is dependent on NO in combination with endothelium-derived hyperpolarizing factor (EDHF). Additionally, our results indicated that extracellular Ca(2+) has an important role on the endothelium-dependent vasodilator effect induced by GSE.

L-Arginine is the precursor of NO (nitric oxide), a key endogenous mediator involved in endothelium-dependent vascular relaxation and platelet function. Although the concentration of intracellular L-arginine is well above the Km for NO synthesis, in many cells and pathological conditions the transport of L-arginine is essential for NO production (L-arginine paradox). The present study was designed to investigate the modulation of L-arginine/NO pathway in systemic arterial hypertension. Transport of L-arginine into RBCs (red blood cells) and platelets, NOS (NO synthase) activity and amino acid profiles in plasma were analysed in hypertensive patients and in an animal model of hypertension. Influx of L-arginine into RBCs was mediated by the cationic amino acid transport systems y+ and y+L, whereas, in platelets, influx was mediated only via system y+L. Chromatographic analyses revealed higher plasma levels of L-arginine in hypertensive patients (175+/-19 micromol/l) compared with control subjects (137+/-8 micromol/l). L-Arginine transport via system y+L, but not y+, was significantly reduced in RBCs from hypertensive patients (60+/-7 micromol.l(-1).cells(-1).h(-1); n=16) compared with controls (90+/-17 micromol.l(-1).cells(-1).h(-1); n=18). In human platelets, the Vmax for L-arginine transport via system y+L was 86+/-17 pmol.10(9) cells(-1).min(-1) in controls compared with 36+/-9 pmol.10(9) cells(-1).min(-1) in hypertensive patients (n=10; P<0.05). Basal NOS activity was decreased in platelets from hypertensive patients (0.12+/-0.02 pmol/10(8) cells; n=8) compared with controls (0.22+/-0.01 pmol/10(8) cells; n=8; P<0.05). Studies with spontaneously hypertensive rats demonstrated that transport of L-arginine via system y+L was also inhibited in RBCs. Our findings provide the first evidence that hypertension is associated with an inhibition of L-arginine transport via system y+L in both humans and animals, with reduced availability of L-arginine limiting NO synthesis in blood cells.

The possible involvement of the endothelium in the vasodilator action of eugenol was investigated in the mesenteric vascular bed (MVB) of the rat. Bolus injections of eugenol (0.2, 2 and 20 micromol) and acetylcholine (ACh; 10, 30 and 100 pmol) induced dose-dependent vasodilator responses in noradrenaline-precontracted beds that were partially inhibited by pretreatment of the MVB with deoxycholate (1 mg mL(-1)) to remove the endothelium (approximately 14% and approximately 30% of the control response remaining at the lowest doses of ACh and eugenol, respectively). The vasodilator effect of glyceryl trinitrate (1 micromol) was unaltered by deoxycholate. In the presence of either N(omega)-nitro-L-arginine methyl ester (300 microM) or tetraethylammonium (1 mM)the response to ACh was partially reduced, whereas eugenol-induced vasodilation was unaffected. Similarly the vasodilator effect of eugenol was not inhibited by indometacin (3 microM). Under calcium-free conditions the vasoconstrictor response elicited by bolus injections of noradrenaline (10 nmol) was dose-dependently and completely inhibited by eugenol (0.1-1 mM). Additionally, the pressor effects of bolus injections of calcium chloride in potassium-depolarized MVBs were greatly reduced in the presence of eugenol (0.1 mM), with a maximal reduction of approximately 71% of the control response. Our data showed that eugenol induced dose-dependent, reversible vasodilator responses in the rat MVB, that were partially dependent on the endothelium, although apparently independent of nitric oxide, endothelium-derived hyperpolarizing factor or prostacyclin. Furthermore, an endothelium-independent intracellular site of action seemed likely to participate in its smooth muscle relaxant properties.

Cumulative evidence suggests that moderate wine consumption exerts a cardioprotective effect. We investigated the occurrence of an antihypertensive effect of an alcohol-free hydroalcoholic grape skin extract (GSE) obtained from skins of a vinifera grape (Vitis labrusca) in experimental rodent hypertension models. The vasodilator effect of GSE (polyphenols concentration 55.5 mg g(-1)) was also assessed in the isolated mesenteric vascular bed of Wistar rats and the antioxidant effect was studied on lipid peroxidation of hepatic microsomes. Oral administration of GSE significantly reduced systolic, mean and diastolic arterial pressure in Wistar rats with desoxycorticosterone acetate-salt and N(G)-nitro-L-arginine methyl ester (L-NAME) induced experimental hypertension. In the rat isolated mesenteric vascular bed pre-contracted with norepinephrine, bolus injections of GSE induced endothelium-dependent vasodilatation that was substantially inhibited by L-NAME, but not by indometacin, tetraethylammonium or glibenclamide. Lipid peroxidation of hepatic microsomes estimated as malondialdehyde production was concentration-dependently inhibited by GSE. In conclusion, the antihypertensive effect of GSE might be owing to a combination of vasodilator and antioxidant actions of GSE. These findings also suggest that the beneficial effect of moderate red wine consumption could be owing to an antihypertensive action induced by compounds occurring in the skin of vinifera grapes.

The effects of aqueous extracts and hydro-alcoholic extract (HAE), and of a dichloromethane fraction (MG1) obtained from the HAE of Mikania glomerata leaves on isolated respiratory and vascular smooth muscle have been investigated. Aqueousextracts and HAE induced a significant inhibition on the histamine contractions on the isolated guinea-pig trachea. HAE extract induced a concentration-dependent relaxation on guinea-pig trachea pre-contracted with histamine (IC50 0.34 (0.29-0.39) mg mL(-1)), acetylcholine (IC50 0.72 (0.67-0.77) mg mL(-1)) or K+ (IC50 1.41 (1.18-1.64) mg mL(-1)) and on isolated human bronchi precontracted with K+ (IC50 0.34 (0.26-0.42) mg mL(-1)). The dichloromethane fraction induced a concentration dependent relaxation in guinea-pig trachea precontracted with K+ (IC50 0.017 (0.012-0.022) mg mL(-1)). The dichloromethane fraction had also a small vasodilator effect on the isolated mesenteric vascular bed and on the isolated rat aorta, and a significant reduction of the oedema induced by subplantar injections of Bothropsjararaca venom in mice. When tested on plasmid DNA, MG1 did not damage the DNA. Chromatographic analysis showed the presence of 11.4% w/w coumarin in MG1. The results supported the indication of M. glomerata products for the treatment of respiratory diseases where bronchoconstriction is present.

The antihypertensive mechanism of alpha2-adrenoceptor agonists, such as clonidine and rilmenidine, is not completely elucidated, although it is probably due to reduction of sympathetic tone mediated by stimulation of central alpha2-adrenoceptors. Because activation of alpha2-adrenoceptors on endothelial cells induces release of endothelium-derived relaxing factor (EDRF), we determined whether nitric oxide (NO) release is involved in the antihypertensive action of clonidine and rilmenidine. In chloralose-anesthetised Wistar rats, systolic and diastolic arterial blood pressures were recorded on a polygraph. Intravenous injection of clonidine or rilmenidine (control group) caused a rapid increase of arterial blood pressure. followed by a long-lasting hypotensive effect. The hypotensive effects, estimated as the area enclosed by the decrease in diastolic pressure during the 20 min after clonidine and rilmenidine injections, were 574+/-60 and 410+/-59 mm Hg/min, respectively. The delta decrease in diastolic arterial blood pressure observed 20 min after intravenous injections of clonidine and rilmenidine was 48+/-5 and 34+/-3 mm Hg, respectively. Clonidine and rilmenidine injected 5-10 min after intravenous pretreatment with L-NAME (2 and 1 mg/kg) or methylene blue (10 mg/kg) induced hypotensive effects that were significantly smaller than that observed for the control group. These results suggest that the antihypertensive effects of clonidine and rilmenidine also may be modulated by the NO-cyclic guanosine monophosphate (cGMP) pathway at the level of the central nervous system and/or at the vascular peripheral circulation.

Pharmacological aspects of mouse hind-paw oedema induced by subplantar injections of Lachesis muta rhombeata (LMR) venom were investigated. The oedema induced by subplantar injections of 10 to 50 ng/g of LMR venom is dose dependent, with onset, peak and duration at 30, 60 and 180 min, respectively. Subplantar injection of 30 ng/g of Bothrops jararaca (BJ) venom induced oedema that has the same intensity as 30 ng/g of LMR venom but lasts for more than 4 h suggesting different time course. Systemic effects or haemorrhage were not observed with doses less than 50 ng/g. Oedema is not due to the presence of oedematogenic amines since dialysis did not change the oedema induced by 30 ng/g of LMR venom. Part of the oedema induced by LMR venom is due to a thermolabile fraction since pre-heating the venom at 100 degrees C for 15 min induced a significant reduction (56.19 +/- 6.8%) of the oedematogenic activity. The oedema induced by LMR venom is possibly induced by release of a pharmacological active substance at the site of injection. Histamine, arachidonate metabolites, nitric oxide and serotonin may play important roles in the oedematogenic effect of LMR venom since pre-treatment of mice with pyrilamine, indomethacin, dexamethasone, L-NAME and methysergide induced a significant reduction (49.86 +/- 10%; 51.06 +/- 5.9%; 77.66 +/- 3.6%; 73.30 +/- 6.1% and 93.77 +/- 2.8%, respectively) of the oedema formation. The present results demonstrate that the oedema induced by LMR and BJ venoms may be triggered and maintained by different pharmacological mechanisms. Since methysergide and L-NAME were the most active inhibitors of the oedema we can suggest that a link between serotonin release by the venom and a NO synthase activation may be an important step in the oedema formation induced by LMR venom.

The effect of terbutaline, a beta2-adrenoceptor stimulator, on the vascular resistance of isolated human placenta was examined. Terbutaline produced no change in basal placental vascular resistance, but when the placental vessels were constricted with angiotensin, terbutaline produced a graded decrease in vascular resistance. The vasodilating effect of a high dose of terbutaline was smaller than the effect 20 microgram of isoprenaline and the effect was significantly blocked by propranolol, a beta-adrenoceptor antagonist. The results suggest that the vasodilating effect of terbutaline on the fetal placental circulation can play a role in the improvement of fetal condition during treatment of premature labour and intrapartum fetal distress.

The preparation and some biochemical properties of a (Na+ + K+)ATPase from male adult Schistosoma mansoni are described. After incubation in a membrane disruption medium, the tegument and carcass of the worms were separated and treated to obtain fractions enriched in (Na+ + K+)ATPase. The activity of the tegumental ouabain sensitive (Na+ + K+)ATPase at 37 C was 20.3 mumole Pi X mg-1 protein X hr-1 and represented 32% of the total ATPase activity. The (Na+ + K+)ATPase prepared from the carcass had a lower specific activity (3.7 mumole Pi X mg-1 protein X hr-1) but a higher relative activity (55%). Similar concentrations of Na+ and K+ activated the enzymes from both sources, and both enzymes were inhibited by similar concentrations of calcium. However, the enzyme from carcass was ten times more sensitive to ouabain than the enzyme from tegument. Comparison with results obtained on the (Na+ + K+)ATPase of human heart showed that the enzymes from the worms were more resistant to ouabain. The half maximal inhibitory concentration of dihydroouabain compared to that of ouabain was also different in the enzymes from human and worm. We conclude that (1) there exists at least one structural difference between the (Na+ + K+)ATPase of S. mansoni and that of the human host, and (2) it is useful to separately study the enzymes from tegument and carcass because they differ in sensitivity to cardiac glycosides.

Electrical stimulation and oxamniquine effect the motor activity of isolated Schistosoma mansoni. Electrical stimulation produced contractions that increased with stimulus intensity. Oxamniquine (10(-4) M) produced an increase in basal tonus and in the frequency and amplitude of the worm's spontaneous contractions. Incubation in the absence of calcium produced a decrease in the basal tonus, abolished the spontaneous contractions of S. mansoni, and abolished the mechanical response induced by electrical stimulation and oxamniquine. The effects of electrical stimulation and oxamniquine were, respectively, significantly reduced and abolished by 10(-6) M verapamil (a calcium channel blocking agent). Bromolysergic acid diethylamide (3 X 10(-5) M), a serotonin blocking agent, reduced the motor response induced by high intensity electrical stimulation and blocked the response induced by oxamniquine. The effects of low intensity electrical stimulation were not modified in the presence of bromolysergic acid. We think that external Ca2+ is important for basal tonus, for spontaneous motor activity, and for motor responses of S. mansoni induced by electrical stimulation and oxamniquine. Serotonin may be important for mechanical responses induced by high intensity electrical stimulation and for responses induced by oxamniquine.

The effect of prostacyclin infusion on the perfusion pressure and on the vasoconstrictor response to three doses of angiotensin II was investigated in six full-term human placentas. The placentas were perfused with a modified Krebs-Henseleit solution and placenta perfusion pressure was recorded. Prostacyclin 5 X 10(-8) M, infused through the foetal placental circulation, produced a significant decrease in placental vascular resistance. The vasodepressor effect of prostacyclin persisted throughout the perfusion period and promptly disappeared when the infusion was stopped. The pressor response of angiotensin II was significantly reduced by prostacyclin infusion. These data suggest an interaction between the vascular effects of prostacyclin and angiotensin II on the placental circulation that might be important in the control of foetal placental blood flow.

The effect of strophantin on isolated guinea-pig ileum was investigated. It was found that strophantin produces a dose-dependent contraction that is not blocked by atropine, ganglionic blockade, but is potentiated by prostigmine. Depolarization of the guinea-pig ileum by a high potassium solution does not change the effect of strophantin. Strophantin response is competitively antagonized by verapamil. The effect is significantly reduced, 5 to 10 min, after the preparation is immersed in zero calcium Tyrode solution. These results support the view that the effect of strophantin is dependent on the influx of calcium through the cell membrane.