The induction of α1-acid glycoprotein by methylmercury

• 1.1. The incorporation of [¹⁴C]leucine into protein was measured in liver preparations and blood of rats following the s.c. administration of methylmercury hydroxide (24 mg/kg body wt) or turpentine (5.0 ml/kg body wt).
• 2.2. The translatability of the RNA obtained from polysomes in an mRNA-dependent reticulocyte lysate was elevated significantly in the preparations derived from the treated rats compared to control rats.
• 3.3. Immunoprecipitation of the labelled translation products or of serum proteins showed that the mRNA activity and the synthesis of α₁-acid glycoprotein, an acute phase reactant, was elevated by the methylmercury treatment as well as by the turpentine-induced inflammatory response.

     

Translation of muscle mRNA in rats following acute exposure to Pb2+ or Cd2+

The hindleg muscle of rats was studied 2 days following the i.p. administration of 0.5 mg Pb2+ /100 g body wt or 0.12 mg Cd2+ /100 g body wt or both Pb2+ and Cd2+. The incorporation of [14C]leucine into proteins was measured using mRNA obtained from the muscle polysomes. The translatability of this poly(A)+ RNA in a mRNA-dependent reticulocyte lysate was elevated similarly in each of the preparations from heavy metal treated rats compared to control rats. Evidence for increased mRNA activity for glyceraldehyde-3-phosphate dehydrogenase and actin was obtained.     

Brain protein synthesis in rabbits following low level aluminium exposure

1. Infant rabbits received s.c.injections 3 times weekly of low doses of aluminium (A1) maltolate (0.5-1.5 mg Al/kg body wt) or aluminium lactate (8 mg Al/kg body wt) from 5 or 10 days of age to 14 or 22 days of age. 2. Brain was used to provide a cell-free protein synthesizing system and this system exhibited increased activity in preparations from Al-exposed infants. The mRNA fraction obtained from the brain polysomal RNA also was more active following Al exposure. 3. The synthesis of immunoprecipitable calmodulin was significantly elevated.     

Induction of hepatic drug metabolizing enzymes by DL-methionine in rats

A single intraperitoneal injection of DL-methionine (500 mg/kg body wt.) to adult male Wistar rats was shown to significantly induce all the components of the hepatic microsomal mixed function oxidase system such as NADPH cytochrome C reductase activity, cytochromes P-450 and b₅, as well as activities of drug metabolizing enzymes such as aminopyrine demethylase and uridine 5′ -diphosphate-glucuronosyltransferase. Combined administration of nicotinamide (250 mg/kg body wt.) and DL-methionine (500 mg/kg body wt.) was shown to bring about an additional increase (25-30%) in the activities of these enzymes as compared to their induction on independent administration of the two endobiotics. In rats bearing Yoshida sarcoma (ascites) tumour as well as in normal rats injected with serum from tumour bearing animals, the decreased activities of hepatic mixed function oxidases could be restored to their normal levels by administration of DL-methionine (500 mg/kg body wt.) to these rats. Whereas actinomycin D (1 mg/kg body wt.) had no effect on the increased incorporation of [¹⁴C] labelled leucine into microsomal proteins following administration of nicotinamide, the enhanced incorporation of the label following DL-methionine administration was completely inhibited by the same dose of actinomycin D. Administration of cycloheximide (0·5 mg/kg body wt.) to rats could completely inhibit the increased incorporation of [¹⁴C] leucine into hepatic microsomal proteins following independent administration of nicotinamide and DL-methionine. Similar inhibitory pattern with actinomycin D and cycloheximide was also demonstrated in case of induction of NADPH cytochromeC reductase activity by both these endobiotics.     

Evaluation of anti-pyretic potential of Ficus racemosa bark.

A study was carried out to evaluate the anti-pyretic effect of a methanol extract of stem bark of Ficus racemosa Linn. (MEFR) on normal body temperature and yeast-induced pyrexia in albino rats. A yeast suspension (10 ml/kg body wt.) increased rectal temperature 19 h after subcutaneous injection. The MEFR, at doses of 100, 200 and 300 mg/kg body wt. p.o., showed significant dose-dependent reduction in normal body temperature and yeast-provoked elevated temperature. The effect extended up to 5 h after drug administration. The anti-pyretic effect of MEFR was comparable to that of paracetamol (150 mg/kg body wt., p.o.), a standard anti-pyretic agent.     

Evaluation of antipyretic potential of Clitoria ternatea L. extract in rats.

The methanol extract of Clitoria ternatea L. root (MECTR) blue flowered variety (Family: Fabaceae), was evaluated for its anti-pyretic potential on normal body temperature and yeast-induced pyrexia in albino rats. Yeast suspension (10 ml/kg body wt.) increased rectal temperature after 19 hours of subcutaneous injection. The extract, at doses of 200, 300 and 400 mg/kg body wt., p.o., produced significant reduction in normal body temperature and yeast-provoked elevated temperature in a dose-dependent manner. The effect extended up to 5 hours after the drug administration. The anti-pyretic effect of the extract was comparable to that of paracetamol (150 mg/kg body wt., p.o.), a standard anti-pyretic agent.     

Agastache mexicana may produce anxiogenic-like actions in the male rat.

Behavioral effects of a water-soluble extract of Agastache mexicana, a plant with purported anxiolytic actions, were studied in male Wistar rats. In the elevated plus-maze test, various doses of the plant extract (3.0 mg/kg body wt.; 9.0 mg/kg body wt.; 12.0 mg/kg body wt.) administered intraperitoneally (i.p.) decreased the exploration of open arms, showing an anxiogenic-like effect. Agastache mexicana (12 mg/kg body wt.; i.p.) did not change immobility in the forced swimming test (i.e., had no anti-depressant effect) but increased the anti-immobility action of 32.0 mg/kg body wt. (i.p.) of desipramine (i.e., increased the antidepressant-like effect of desipramine). A. mexicana had no effect on exploratory activity in an open field test, indicating that it had no sedative effect at the doses used. It is concluded that effects of the water extract of A. mexicana are more consistent with an anxiogenic-like property than an anxiolytic-like one.     

Antiinflammatory and chronic toxicity study of the leaves of Ageratum conyzoides L. in rats

The hydroalcoholic extract (HAE) of Ageratum conyzoides leaves was studied for its antiinflammatory effect on subacute (cotton pellet-induced granuloma) and chronic (formaldehyde-induced arthritis) models of inflammation in rats. The absence or presence of toxicity by prolonged use of HAE was also evaluated through biochemical and hematological analysis of rats blood samples using daily oral doses of 250 or 500 mg/kg body wt., during 90 days. The results showed that the group of rats treated with HAE (250 mg/kg body wt.; p.o.) had a 38.7% (p < 0.05) reduction in cotton-pellet granuloma. The development of chronically induced paw edema was also reduced significantly (p < 0.05) by the plant extract. The toxicity study did not show any treatment-related abnormalities in biochemical and hematological parameters. The biochemical analysis from blood samples drawn from group of rats treated orally with 500 mg/kg body wt. did, however, present 30.2% (p < 0.05) reduction of SGPT activity as compared to the corresponding control group. These results confirm the antiinflammatory properties of A. conyzoides, with no apparent hepatotoxicity.     

Inhibition of testosterone biosynthesis by ethanol. Relation to hepatic and testicular acetaldehyde, ketone bodies and cytosolic redox state in rats.

In experiments in which liver and testis freeze-stops were performed on pentobarbital-anaesthetized rats, ethanol (1.5 g/kg body wt.) reduced plasma testosterone concentration from 13.1 to 3.2 nmol/litre. 4-Methylpyrazole abolished the ethanol-induced hepatic and testicular increase in the lactate/pyruvate ratio, and the testicular acetaldehyde level, but did not diminish the reduction in plasma testosterone concentration. In testes, but not in liver, ethanol decreased the 3-hydroxybutyrate/acetoacetate ratio, and 4-methylpyrazole did not prevent this effect. In experiments in which freeze-stop was performed after cervical dislocation, ethanol decreased the testis testosterone concentration from 590 to 220 pmol per g wet wt. The effects of ethanol and 4-methylpyrazole on testis acetaldehyde, lactate/pyruvate and 3-hydroxybutyrate/acetoacetate ratios were the same as found during anaesthesia. The NAD+-dependent ethanol oxidation capacity in testis ranged from 0.1 to 0.2 mumol/min per g wet wt. and seemed to be inhibited by 4-methylpyrazole both in vivo and in vitro. In additional experiments, ethanol doses between 0.3 and 0.9 g/kg body wt. did not alter the plasma testosterone concentration in rats treated, or not treated, with cyanamide, which induced elevated acetaldehyde levels in blood and testes. The results suggest that ethanol-induced inhibition of testosterone biosynthesis was not caused by extratesticular redox increases, or by extra- or intra-testicular acetaldehyde per se. The inhibition is accompanied by changes in testicular ketone-body metabolism.     

Antihyperglycemic activity of Tarralin™, an ethanolic extract of Artemisia dracunculus L.

The studies reported here were undertaken to examine the antihyperglycemic activity of an ethanolic extract of Artemisia dracunculus L., called Tarralin in diabetic and non-diabetic animals. In genetically diabetic KK-A(gamma) mice, Tarralin treatment by gavage (500 mg/kg body wt./day for 7 days) lowered elevated blood glucose levels by 24% from 479+/-25 to 352+/-16 mg/dl relative to control animals. In comparison, treatment with the known antidiabetic drugs, troglitazone (30 mg/kg body wt./day) and metformin (300 mg/kg body wt./day), decreased blood glucose concentrations by 28% and 41%, respectively. Blood insulin concentrations were reduced in the KK-A(gamma) mice by 33% with Tarralin, 48% with troglitazone and 52% with metformin. In (STZ)-induced diabetic mice, Tarralin treatment, (500 mg/kg body wt./day for 7 days), also significantly lowered blood glucose concentrations, by 20%, from 429+/-41 to 376+/-58 mg/dl relative to control. As a possible mechanism, Tarralin was shown to significantly decrease phosphoenolpyruvate carboxykinase (PEPCK) mRNA expression by 28% in STZ-induced diabetic rats. In non-diabetic animals, treatment with Tarralin did not significantly alter PEPCK expression, blood glucose or insulin concentrations. The extract was also shown to increase the binding of glucagon-like peptide (GLP-1) to its receptor in vitro. These results indicate that Tarralin has antihyperglycemic activity and a potential role in the management of diabetic states.     

Antihypercholesterolemic and antioxidative effects of an extract of the oyster mushroom, Pleurotus ostreatus, and its major constituent, chrysin, in Triton WR-1339-induced hypercholesterolemic rats

Hypercholesterolemia and oxidative stress are known to accelerate coronary artery disease and progression of atherosclerotic lesions. In the present study, an attempt was made to evaluate the putative antihypercholesterolemic and antioxidative effects of an ethanolic extract of the oyster mushroom (Pleurotus ostreatus) and chrysin, one of its major components, in hypercholesterolemic rats. Hypercholesterolemia was induced in rats by a single intraperitoneal injection of Triton WR-1339 (300 mg/kg body weight (b.wt.)), which resulted in persistently elevated blood/serum levels of glucose, lipid profile parameters (total cholesterol, triglycerides, low-density lipoprotein-, and very low-density lipoprotein-cholesterol), and of hepatic marker enzymes (alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, and lactate dehydrogenase). In addition, lowered mean activities of hepatic antioxidant enzymes (catalase, superoxide dismutase, and glutathione peroxidase) and lowered mean levels of nonenzymatic antioxidants (reduced glutathione, vitamin C, and vitamin E) were observed. Oral administration of the mushroom extract (500 mg/kg b.wt.) and chrysin (200 mg/kg b.wt.) to hypercholesterolemic rats for 7 days resulted in a significant decrease in mean blood/serum levels of glucose, lipid profile parameters, and hepatic marker enzymes and a concomitant increase in enzymatic and nonenzymatic antioxidant parameters. The hypercholesterolemia-ameliorating effect was more pronounced in chrysin-treated rats than in extract-treated rats, being almost as effective as that of the standard lipid-lowering drug, lovastatin (10 mg/kg b.wt.). These results suggest that chrysin, a major component of the oyster mushroom extract, may protect against the hypercholesterolemia and elevated serum hepatic marker enzyme levels induced in rats injected with Triton WR-1339.     

Evaluation of anti-pyretic potential of Jussiaea suffruticosa L. extract in rats.

A study was carried out to evaluate the anti-pyretic potential of the methanol extract of the aerial part of Jussiaea suffruticosa Linn. (MEJS) on normal body temperature and yeast-induced pyrexia in albino rats. Yeast suspension (10 ml/kg body wt.) increased rectal temperature after 19 hours of subcutaneous injection. The MEJS, at doses of 100, 200 and 300 mg/kg body wt. p.o., showed significant reduction in normal body temperature and yeast-provoked elevated temperature in a dose-dependent manner. The effect also extended up to 5 hours after the drug administration. The anti-pyretic effect of MEJS was comparable to that of paracetamol (150 mg/kg body wt, p.o.), a standard anti-pyretic agent.     

Effect of Calotropis procera latex on isoproterenol induced myocardial infarction in albino rats.

The alcoholic extract of the latex obtained from Calotropis procera (Asclepidaceae) was evaluated for protection against isoproterenol (20 mg/100 g body wt., s.c.)-induced myocardial infarction in albino rats. The heart damage induced by isoproterenol was indicated by elevated levels of the marker enzymes such as Creatine Kinase-isoenzyme (CK-MB), Lactate dehydrogenase (LDH), Serum Glutamate Oxaloacetic Transaminase (SGOT) and Serum Glutamate Pyruvate Transaminase (SGPT) in serum with increased lipid peroxide and reduced glutathione content in heart homogenates. Microscopical examination (histopathology) was also performed on the myocardial tissue. Pretreatment with an ethanolic latex extract of Calotropis procera at a dose of 300 mg/kg body wt., administered orally thrice a day for 30 days, reduced significantly (p < 0.01) the elevated marker enzyme levels in serum and heart homogenates in isoproterenol-induced myocardial infarction. Histopathological observation revealed a marked protection by the extract in myocardial necrotic damage.     

Toxicity of endosulfan on kidney of male rats in relation to drug metabolizing enzymes and microsomal lipid peroxidation

Endosulfan administration (po, 15 and 30 days at 7.5 and 10 mg/kg body wt respectively) inhibited the activity of microsomal mixed function oxidases in kidney tissue of male rats. Microsomal and cytosolic protein contents of kidney were significantly increased following 30 days endosulfan exposures. Profound induction in the activity profiles of alcohol dehydrogenase and cytosolic glutathione s-transferase was noticed, however, no such change was apparent in the activity of aldehyde dehydrogenase. Microsomal preparations from treated animals showed a dose and duration dependent increase in spontaneous lipid peroxidation. The observed biochemical changes persisted even after 7 days normalcy allowance provided after the endosulfan (10 mg/kg body wt) withdrawl. The results suggest a substantial renal toxicity of endosulfan to male rats in relation to microsomal mixed function oxidases and associated functions which possibly resulted from lipid peroxidative damage of microsomal membrane in treated animals.     

Modulating effect of aqueous extract of telfairia occidentalis on induced cyanide toxicity in rats

The effect of lyophilised aqueous extract of Telfairia occidentalis (TO) on induced cyanide toxicity in rats was investigated. Twenty 3-week old male wistar albino rats were randomly distributed into one control and three treatment groups of five rats each: control group (group1), group treated with 3mg/kg body wt of cyanide only (group2), group treated with 3mg/kg body wt. each of cyanide and extract (group3), and a group treated with 3mg/kg Body wt of extract only (group4) were used for the investigation. Cyanide toxicity reduced both food and water intake, while the food intake was improved in group3, this effect of the extract on food was not observed on water intake. Cyanide reduced average body weight of rats significantly. The reduction effect of cyanide on body weight was countered by Telfairia occidentalis extract. The extract did not have an observable effect on rats' body weight. Ocular lesion was observed in 67% of rats in group2 . This ocular effect of cyanide was mitigated significantly by Telfairia occidentalis as only 17% of the rats in group3 had ocular lesion. Cyanide toxicity produced nasal discharge in 39% of the rat population in group2 while there was a partial but considerable reduction (21%) in the severity of nasal discharge in group 3. There was no significant difference in the organ/body wt.ratio between the treatments and the control groups for all the organs examined in the study. Biochemical analysis of liver enzymes showed that cyanide (group2) damaged the liver as there was significantly elevated presence of Aspartate aminotransferase (AST) and Alanine aminotransferase (ALP) above those of the control group. The damaging effect of cyanide on the liver was ameliorated by Telfairia occidentalis considerably.Histopathological effect of cyanide toxicity on the organs examined included multifocal degeneration and necrosis of the liver, mild kidney congestion and congestion of the brain. These effects were moderated mildly by Telfairia occidentalis. Group 4, treated with the vegetable alone had none of the observed histopathology in the organs examined. We concluded that lyophilised aqueous extracts of Telfairia occidentalis showed good potential as a safe antidote for cyanide poisoning when administered concomitantly or very shortly after ingestion of sub-lethal dose of cyanide. However, further bioassay guided fractionation and analytical studies are needed to identify the actual chemical compound or molecule in the vegetable responsible for or associated with the observed effects.     

Studies of the ethylation of rat liver transfer ribonucleic acid after administration of l-ethionine

1. The ethylated nucleosides present in tRNA isolated from the livers of rats treated with 0.5g of l-ethionine/kg body wt. were investigated. Evidence that this tRNA contained N(2)-ethylguanine, N(2)N(2)-diethylguanine, N(2)-ethyl-N(2)-methylguanine, 7-ethylguanine, two ethylated pyrimidines and ethylated ribose groups was obtained. 2. Ethylation of bacterial tRNA was catalysed by extracts containing tRNA methylases prepared from rat liver by using S-adenosyl-l-ethionine as an ethyl donor, but the rate of ethylation was 20 times less than the rate of methylation with S-adenosyl-l-methionine as a methyl donor. 3. The principal product of such ethylation in vitro was N(2)-ethylguanine and traces of the other ethylated guanines and pyrimidines found in tRNA isolated from rats treated with ethionine in vivo were also found. 1-Ethyladenine was not formed, although 1-methyl-adenine is a major product of methylation of bacterial tRNA by these extracts, and 1-ethyladenine was not present in the rat liver tRNA isolated from ethionine-treated animals. 4. After injection of actinomycin D (15mg/kg body wt.) or l-methionine (1.0g/kg body wt.) before the ethionine, ethylation of tRNA was diminished by about 80% but not completely abolished. Administration of 1-aminocyclopentanecarboxylic acid (2.5g/kg body wt.) to inhibit the formation of S-adenosyl-l-ethionine inhibited ethylation of tRNA by 44%. 5. These results suggest that not all of the ethylation of tRNA that occurs in the livers of rats treated with ethionine is mediated by the action of tRNA methylases acting with S-adenosyl-l-ethionine as a substrate, but that this pathway does occur and accounts for a major part of the observed ethylation. 6. The results are discussed with reference to ethionine-induced hepatocarcinogenesis.     

The relative importance of glutathione and metallothionein on protection of hepatotoxicity of menadione in rats.

The effects of induction of metallothionein (MT) on the toxicity of menadione were investigated in rat liver slices. The protective role of hepatic glutathione (GSH) was also studied and compared to that of MT. A 3-h incubation of rat liver slices with menadione (100-300 microM) containing medium (37 degrees C, pH 7.4, 95%O2:5%CO2) resulted in cellular toxicity, as shown by changes in cytosolic K, Ca and GSH concentrations and lactate dehydrogenase (LDH) leakage. A dose-dependent decrease in cytosolic K and GSH was observed concomitant with an increase in cytosolic Ca and LDH leakage after incubation with menadione. Pretreatment of rats with zinc sulphate (ZnSO4) (30 mg/kg body wt.) increased MT levels in liver slices and suppressed the toxicity of menadione. Intracellular GSH concentrations in liver slices were either depleted or increased by injection of rats with buthionine sulfoximine (BSO), (4 mmol/kg body wt.) and N-acetyl-L-cysteine (NAC) (1.6 g/kg body wt.), respectively. Intracellular GSH was found to be crucial in protection against menadione toxicity. Menadione toxicity was increased when the rats were injected with sodium phenobarbital (PB) (4 x 80 mg/kg body wt.). Pretreatment with Zn provided partial protection against menadione toxicity in liver slices from both BSO- and PB-injected rats. These findings suggest that induction of MT synthesis does protect against quinone-induced toxicity, but the role may be secondary to that of GSH. The mechanisms by which MT protect against menadione toxicity are still unclear but may involve protection of both redox cycling and sulphydryl arylation.     

Effects of vitamin C on the hypobaric hypoxia-induced immune changes in male rats

Hypobaric hypoxia (HH) induces oxidative stress (OS) and is associated with the generation of reactive oxygen species (ROS). Vitamin C is an efficient antioxidant, and it is used in a high-altitude environment to reduce the OS. The present study explores the role of vitamin C on some HH-induced changes of immune parameters in rats which were exposed to HHc condition at 18,000 ft in a simulated chamber for 8 h/day for 6 days with and without vitamin C administration at three different doses (200, 400, and 600 mg/kg body wt). The phagocytic activity of circulating blood WBC was increased, and the cytotoxic activity of splenic mononuclear cell (MNC) and the delayed type of hypersensitivity (DTH) responses to bovine serum albumin (BSA) were decreased in rats exposed to HHc condition, but these immune changes were blocked after administration of vitamin C at 400 mg/kg body wt. The leukocyte adhesive inhibition index (LAI) was not altered either in HHc condition or after administration of vitamin C in HHc condition. The serum corticosterone (CORT) concentration was increased in rats exposed to HHc condition which was blocked after administration of vitamin C (400 mg/kg body wt). The immune parameters and serum CORT concentration, however, did not show any recovery after administration of vitamin C at the dose of 200 and 600 mg/kg body wt. The present study indicates that administration of vitamin C at a dose of 400 mg/kg body wt may prevent the HH-induced immunological changes but not at the lower dose (200 mg/kg body wt) or higher dose (600 mg/kg body wt) in rats.     

Quercetin as a prophylactic measure against high altitude cerebral edema

The present study was undertaken to elucidate the intervention of quercetin against high altitude cerebral edema (HACE) using male Sprague Dawley rats as an animal model. This study was also programmed to compare and correlate the effect of both quercetin (flavonoid) and dexamethasone (steroid) against HACE. Six groups of animals were designed for this experiment, (I) normoxia, (II) hypoxia (25,000ft, 24h), (III) normoxia+quercetin (50mg/kg body wt), (IV) normoxia+dexamethasone (4mg/kg body wt), (V) hypoxia+quercetin (50mg/kg body wt), (VI) hypoxia+dexamethasone (4mg/kg body wt). Quercetin at 50mg/kg body wt, orally 1h prior to hypoxia exposure, was considered as the optimum dose, due to a significant reduction in the level of brain water content and cerebral transvascular leakage (P<0.001), as compared to control (24h hypoxia). Dexamethasone was administered at 4mg/kg body wt, orally, 1h prior to hypoxia exposure. Both drugs (quercetin and dexamethasone) could efficiently reduce the hypoxia-induced hematological changes. Quercetin was observed to be a more potent antioxidative and anti-inflammatory agent. It blocks nuclear factor kappa-beta (NFκB) more significantly (P<0.05) than the dexamethasone-administered hypoxia-exposed rats. Histopathological findings demonstrate the absence of an edema and inflammation in the brain sections of quercetin-administered hypoxia-exposed rats. The present study reveals quercetin to be a potent drug against HACE, as it efficiently attenuates inflammation as well as cerebral edema formation without any side effects of steroid therapy (dexamethasone).     

Endothelium-derived nitric oxide is involved in the hypotensive and vasorelaxant responses induced by the aqueous fraction of the ethanolic extract of the leaves of Albizia inopinata (Harms) G. P. Lewis in rats.

The acute cardiovascular effects of an aqueous fraction of the ethanolic extract of the leaves (AFL) of Albizia inopinata (Harms) G. P. Lewis (Leguminosae) were studied in rats using a combined in vivo and in vitro approach. In conscious, unrestrained rats, AFL (5, 10 and 20 mg/kg(-1) body wt. i.v., randomly) produced a significant and dose-dependent hypotension associated with increases in heart rate and cardiac output, and with a strong reduction in total peripheral resistances. The hypotensive response to AFL (20 mg/kg(-1) body wt.) was attenuated significantly after nitric oxide (NO) synthase blockade (L-NAME, 20 mg/kg(-1) body wt. i.v.). Furthermore, under these conditions, the associated tachycardia was inhibited completely. In isolated rat aortic rings, increasing concentrations of AFL (10, 20, 40 and 80 microg/ml(-1)) were able to antagonize the effects of phenylephrine- (1 microM) and KCl- (80 mM) induced contractions (IC50 value 65 +/- 4 and 54 +/- 6 microg/ml(-1), respectively). The smooth muscle-relaxant activity of AFL was inhibited similarly either removal of the vascular endothelium or by L-NAME (10 and 100 microM), but was not affected significantly by atropine (1 microM) or indomethacin (10 microM). In isolated rat atrial preparations, AFL (30, 100, 300 and 500 microg/ml(-1)) produced concentration-related negative inotropic and chronotropic effects (IC50 value = 274 +/- 53 and 335 +/- 23 microg/ml(-1), respectively). These results suggest that in rats, the hypotensive effect of AFL is due to a peripheral vasodilation, at least partly secondary to the release of NO by the vascular endothelium. The direct cardio-depressant actions of AFL are of little importance in the systemic effects of the extract.