Animal models to test drugs with potential antidiabetic activity.

Although medicinal plants have been historically used for diabetes treatment throughout the world, few of them have been validated by scientific criteria. Recently, a large diversity of animal models has been developed to better understand the pathogenesis of diabetes mellitus and new drugs have been introduced in the market to treat this disease. The aim of this work was to review the available animal models of diabetes and some in vitro models which have been used as tools to investigate the mechanism of action of drugs with potential antidiabetic properties. In addition, a MEDLINE/PUBMED search for articles on natural products, pancreatectomy and diabetes mellitus treatment published between 1996 and 2006 was done. In the majority of the studies, natural products mainly derived from plants have been tested in diabetes models induced by chemical agents. This review contributes to the researcher in the ethnopharmacology field to designs new strategies for the development of novel drugs to treat this serious condition that constitutes a global public health.

The puzzle of asthma treatment: animal models to genetic studies.

The recognition that asthma is an inflammatory disease opens a new field to find effective models for the evaluation and development of new drugs. In this scenario, many novel candidate molecules have been shown to work perfectly in animal models, but not in clinical studies. Ancillary models are reviewed in association with the findings obtained in either transgenic or knockout mice. In parallel, genetic studies in animal models and human populations have identified several genes that are asthma-related. Knowledge of these recent findings, in parallel with pharmacogenomic studies will be necessary to direct new strategies for the development of novel drugs to treat subgroups of patients with asthma.

Effect of protein kinase C and calcium on bradykinin-mediated contractions of rabbit vessels.

Bradykinin caused graded contractions of rings of rabbit aorta and jugular vein with EC50 values of 1.3 microM and 2.2 nM. In denuded preparations, responses of bradykinin in jugular vein but not in aorta were potentiated 1,000-fold. Both preparations bathed in calcium-free solution showed markedly depressed responses to bradykinin, but addition of 1 mM EGTA further inhibited bradykinin responses only in aorta. Time-course experiments carried out in calcium-free solution plus EGTA revealed that bradykinin contractions in rabbit aorta were very sensitive to extracellular calcium, whereas responses of the jugular vein depended on both extracellular and intracellular calcium sources. Responses to bradykinin in both tissues were unaffected by nicardipine (1 microM) but were partially antagonized by NiCl2 (0.1-0.3 mM). Ryanodine (30 microM) incubated in calcium-free medium markedly inhibited jugular vein responses to bradykinin but had no effect on aortic responses. Phorbol ester (1 microM) caused a slow tonic contraction in jugular vein but not in aorta and inhibited bradykinin responses in the former preparation. Staurosporine (1-100 nM) and 1-(5-isoquinolinesulfonyl)-2-methylpiperizine (H-7, 3 and 10 microM) caused a dose-dependent inhibition of bradykinin-induced contractions in jugular vein but were less effective in aorta.(ABSTRACT TRUNCATED AT 250 WORDS)

In vitro effects of calcium entry blockers, chlorpromazine and fenoterol upon human pregnant myometrium contractility.

The inhibitory effects of nifedipine, verapamil, cinnarizine (calcium entry blockers), chlorpromazine (a putative calmodulin antagonist) and fenoterol (a beta 2-adrenoceptor agonist) on contractility in human isolated pregnant myometrium were studied. Spontaneous contractions (present in 93% of the preparations) were inhibited in a concentration-related manner by these compounds in the following order of potency: nifedipine greater than verapamil much greater than cinnarizine greater than chlorpromazine. Cinnarizine was effective only at a concentration greater than 100 microM. Fenoterol, at 10 microM, did not produce an inhibitory effect but decreased the frequency of spontaneous contractions. All drugs, except fenoterol, produced a concentration-dependent relaxation of K+-induced contractions in the following order of sensitivity: nifedipine greater than verapamil much greater than chlorpromazine. Cinnarizine produced only about 40% of relaxation. Under these conditions nifedipine and verapamil were about 80 and 5 fold more potent respectively than when tested against spontaneous contractions. The potencies of chlorpromazine and cinnarizine did not differ in the two experimental conditions. Both the spontaneous and K+-induced contractions were inhibited in a time-dependent manner in Ca2+-free media and the responses were almost completely abolished in 70-100 min. Calcium addition to the medium rapidly restored both spontaneous or K+-induced contractions. To investigate further the role of intracellular calcium, K+-depolarized preparations contracted by calcium 3 mM (40-60% of maximal contractions) were relaxed by these compounds. Nifedipine and verapamil showed a relaxation time course similar to that induced by calcium removal. Cinnarizine and fenoterol had no relaxant effect while chlorpromazine induced a slight and slow relaxation. 6 These findings suggest that calcium influx and calmodulin are involved in spontaneous contractions of pregnant human myometrium in vitro. Since nifedipine and verapamil were more potent against K+-induced than spontaneous contractions, calcium channels activated by these conditions could be different. Finally, fenoterol, a beta 2-adrenoceptor agonist, widely used as a tocolytic agent, blocked neither spontaneous nor K+-induced contractions.

Anti-inflammatory effects of theophylline, cromolyn and salbutamol in a murine model of pleurisy.

1. The aim of this study was to examine the effect of theophylline, cromolyn and salbutamol, three well-known anti-asthmatic drugs, on the early (4 h) and late (48 h) phases of cell migration and fluid leakage induced by carrageenin in the pleural cavity of mice. 2. In the first set of experiments, animals were pretreated (30 min) with different doses of theophylline (0.5-50 mg kg-1, i.p.), cromolyn (0.02-0.2 mg per pleural cavity) or salbutamol (0.05-50 mg kg-1, i.p.); the total and differential cell content, and also the exudate were analysed 4 h after carrageenin (1%) administration. Afterwards, in order to evaluate the time course effects of these drugs on both phases of the inflammatory reaction, one dose employed in the above protocol was chosen, to pretreat (0.5-24 h) different groups of animals. The studied parameters were evaluated 4 and 48 h after pleurisy induction. 3. Acute administration of theophylline (1-50 mg kg-1, i.p.) cromolyn (0.02-0.2 mg per pleural cavity) and salbutamol (0.5-50 mg kg-1, i.p.), 30 min prior to carrageenin, caused significant inhibition of total cell and fluid leakage in the pleural cavity at 4 h (P < 0.01). All drugs exerted a long-lasting inhibitory effect on both exudation and cell migration (P < 0.01) when administered 0.5-8 h before pleurisy induction. However, the temporal profile of the inhibitory effect induced by these drugs on the first phase of the inflammatory reaction was clearly different. Thus, the inhibitory effect induced by theophylline and cromolyn on exudation was significantly longer (up to 24 h) in comparison to their effects on cell migration (only up to 8 h). In contrast, although salbutamol when administered 30 min before pleurisy induction abolished fluid leakage (P < 0.01), this effect was not sustained in the groups pretreated for 4-8 h. In these latter groups, a significant but much smaller reduction of exudation was observed (P < 0.01), whereas the magnitude of cell migration inhibition did not vary. 4. The second phase (48 h) of the inflammatory reaction induced by carrageenin (1%) was significantly inhibited by cromolyn (0.02 mg per pleural cavity) when this drug was administered 0.5-24 h before pleurisy induction (P < 0.01). Similar results were observed when theophylline (50 mg kg-1, i.p.) was administered 0.5-4 h before the injection of the phlogistic agent (P < 0.01). Treatment of the animals with salbutamol (5 mg kg-1, i.p.), 0.5-24 h before pleurisy induction, did not inhibit either cell migration or fluid leakage. In this condition, a significant increase of these parameters was observed in the group pretreated with salbutamol 8-24 h before pleurisy induction (P < 0.01). 5. These results indicate that theophylline and cromolyn were able to inhibit the early (4 h) and late (48 h) phases of the inflammatory reaction induced by carrageenin in a murine model of pleurisy. Salbutamol was effective only against the early phase. The inhibitory effects of theophylline, cromolyn and salbutamol on the early phase of this inflammatory reaction were long-lasting, although a distinct profile of inhibition was observed among them. These findings confirm and extend previous results described in other models of asthma and support both clinical and experimental evidence suggesting that these anti-asthmatic agents exhibit marked anti-inflammatory properties.

Propranolol and hyperthyroidism: serum free fatty acids and glucose-induced insulin release in nondiabetic thyrotoxic patients during treatment to clinical compensation.

Glucose-induced insulin secretion was studied in 10 hyperthyroid patients, without personal or familial diabetic background, treated with increasing weekly doses of propranolol until clinical compensation was obtained. Intravenous glucose tolerance tests (25g) with concomitant determination of serum glucose, insulin and FFA were done before treatment, at 240 mg/day of propranolol and after clinical compensation. Patients were divided into two groups according to laboratory data and propranolol dosage needed for clinical compensation (group A: 240 mg/day; group B: 320-400 mg/day). Fasting serum insulin, glucose disappearance rate, and estimates of total insulin secretion after intravenous glucose did not change significantly during propranolol therapy and were within the normal range. Fasting FFA of untreated patients were significantly higher than control values (p less than 0.001), but a significant decrease was already seen at 240 mg/day of propranolol, even before clinical compensation. There was a marked difference in the insulin secretion pattern of thyrotoxic patients as compared to controls. Serum insulin and insulin:glucose ratios increased promptly, and at 5 min after glucose reached significantly higher levels than in normal subjects, before treatment as well as after clinical compensation with the propranolol therapy. Both the increased levels of FFA and of T3 could be involved in this pattern of the insulin response of nondiabetic thyrotoxic patients, since the secretion of insulin during the first 10 min after intravenous glucose was directly correlated to fasting serum FFA before propranolol, and serum T3 was directly correlated with total insulin response after clinical compensation. Furthermore the comparison of the results obtained in group A and group B patients raises the possibility that an increased beta-cell responsiveness to beta-adrenergic stimuli might also be involved in this pattern of insulin secretion.

Analysis of the inflammatory response induced by substance P in the mouse pleural cavity.

This study analyzes both cell migration and exudation responses elicited by substance P (SP) in the mouse pleural cavity. SP caused, 4 h after its administration into the mouse pleural cavity, a dose-related recruitment of leukocytes (ED50 = 14.2 nmol), mainly due to mononuclears. Leukocytes peaked between 2 and 4 h, being followed by a slight decay that remained elevated for up to 24 h. Exudation, although small, was significantly elevated from 2 to 96 h after. NK1 (FK 888) or NK3 (SR 142801), but not NK2 (SR 48968) tachykinin receptor antagonists, significantly inhibited cell migration. HOE 140 and NPC 17731, bradykinin B2 receptor antagonists, caused graded inhibition of cell influx (ID50s of 0.03 and 0.04 pmol), but des-Arg9-Leu8-BK, B1 receptor antagonist, had no effect. The nitric oxide inhibitors L-NOARG and L-NAME, but not D-NAME, significantly inhibited SP-induced pleurisy. Pretreatment of the animals with indomethacin, dexamethasone, terfenadine, theophylline or salbutamol produced significant inhibition of the inflammatory parameters, whereas cromolyn only inhibited exudation. These results indicate that intrapleural injection of SP in mice elicit a long-lasting inflammatory reaction that is characterized by the participation of nitric oxide, kinins, cyclooxygenase metabolites and histamine. Antiasthmatic drugs such as theophylline, salbutamol, dexamethasone, and, to a lesser extent cromolyn, also markedly inhibit this inflammatory reaction. These results provide clear evidence supporting the role played by SP in neurogenic inflammation.

Effects of anti-inflammatory drugs upon nitrate and myeloperoxidase levels in the mouse pleurisy induced by carrageenan.

The effects of several drugs (terfenadine, bradykinin B2 receptor antagonists: HOE 140, NPC 17731, diacerein, indomethacin, meloxicam, nabumetone, and dexamethasone) upon myeloperoxidase and nitrate levels were analyzed in an inflammation model characterized by biphasic peaks (4 and 48 h) of cell migration and of fluid leakage. Myeloperoxidase levels were significantly higher only in the first phase (4 h; median and range; 537.5; 323.6-683.7 mU/ml; P < 0.01), whereas increased mean nitrate levels were detected in both phases (4 h: 19.0; 6.2-32 microM and 48 h: 13.7; 8.9-17.8 microM; P < 0.01). Enhancement of both cell migration and myeloperoxidase levels, 4 h after pleurisy induction, was effectively inhibited by all studied drugs. All of them, except diacerein also inhibited exudation. At this time, nabumetone and diacerein also significantly reduced nitrate levels (P < 0.01). Regarding the second phase (48 h), although dexamethasone, diacerein, and terfenadine decreased either cell migration or exudation, no drugs caused any change in the levels of nitrate. These results indicate that the degree of inhibition of the tested drugs upon the parameters studied do not match, suggesting that differences in these effects may certainly interfere with their efficacy.

Analysis of the mechanisms underlying the biphasic responses to bradykinin in circular muscle from guinea pig ileum.

Experiments were designed to further characterize the receptor mediating the biphasic response to bradykinin in circular muscle from guinea pig ileum in vitro by the use of HOE 140, a potent and specific bradykinin antagonist. D-Arg-[Hyp3,Thi5,D-Tic7,Oic8]bradykinin (HOE 140, 0.1-1000 nM) caused a graded inhibition of bradykinin (10 nM)-induced contraction and relaxation responses in circular muscle from guinea pig ileum, with IC50s of 4 and 10 nM respectively. However, the potency of HOE 140 to antagonize the bradykinin (300 nM)-induced contraction and relaxation was decreased about 6-fold (IC50 22 nM) and 57-fold (IC50 570 nM). HOE 140 (3-100 nM) caused parallel and concentration-dependent rightward displacements of bradykinin (0.1-3000 nM)-induced biphasic concentration-response curves in circular muscle from guinea pig ileum. Schild regression plots yielded straight lines with slopes not significantly different from unity and pKb values of 9.0 and 8.7 against bradykinin-induced contraction and relaxation, respectively. Similar pKb values (8.7) were obtained for HOE 140 against bradykinin-mediated contraction in the longitudinal muscle of the guinea pig ileum. The action of HOE 140 was selective for bradykinin, since response to other agonists were not affected. It is concluded that HOE 140 does not discriminate the receptors mediating the biphasic responses to bradykinin in circular muscle from guinea pig ileum, as it showed a similar selective, competitive and reversible antagonism against both components of the bradykinin response in this preparation.

Pro-inflammatory effects induced by bradykinin in a murine model of pleurisy.

Bradykinin caused a dose-related increase in cell influx 4 h after its administration into the mouse pleural cavity (ED50 = 3.2 nmol/cav., 95% confidence limits = 0.6-15.5). Cell influx peaked at 4 h and remained elevated for up to 72 h, whereas exudation was detected between 2 and 6 h after bradykinin administration. Both HOE 140 (D-Arg-[Hyp3,Thi5,D-Tic7, Oic8]bradykinin) and NPC 17731 (D-Arg0-[Hyp3 D-HypE(transpropyl7)Oic8]bradykinin) inhibited bradykinin-induced cell influx (ID50 0.028 (0.05-0.16) and 0.4 (0.3-0.7) pmol/cav., respectively). Des-Arg9-[Leu8]bradykinin (0.1 and 3.0 nmol/cav., 30 min before) did not inhibit the effects of bradykinin. Pre-treatment of animals with either indomethacin, terfenadine, dexamethasone, N(omega)-nitro-L-arginine benzyl ester, cromolyn, theophylline, salbutamol, FK 888 (N2-[(4R)-4-hydroxy-1-(1-methyl-1H-indol-3-yl)carbonyl-L-propyl]N-met hyl-N-phenyl-methyl-3-(2-naphthyl)-L-alaninamide) or SR 142801 ((N)-(1-[3-[1-benzoyl-3-(3,4-dichloro-phenyl)-piperidin-3-yl]pr opy l]-4-phenyl-piperidin-4-yl)-N-methyl-acetamide) significantly inhibited cell migration (P < 0.01). These results indicate that bradykinin had a significant pro-inflammatory effect on the pleural cavity of the mice. This effect seems to be primarily mediated via activation bradykinin B2 receptors which trigger the release of other mediators.

Bradykinin-induced biphasic response in the rat isolated stomach fundus: functional evidence for a novel bradykinin receptor.

The responses of the rat isolated stomach fundus to bradykinin (BK) and des-Arg9-BK (DA-BK) have been examined. In rat isolated stomach fundus pre-contracted with BaCl2 (0.5-1 mM), BK caused concentration-dependent biphasic responses characterized by relaxation followed by contraction. DA-BK also caused marked relaxations, but, unlike BK, induced only small contractions. Removal of the mucosal layer initially abolished the relaxant responses to BK and both responses to DA-BK without affecting BK-induced contractions, but repeated challenges with BK or DA-BK revealed a time-dependent reappearance of the relaxant response, suggesting "de novo" synthesis of BK receptors. Pretreatment of rat stomach fundus with tetrodotoxin (1 microM), atropine (1 microM), captopril (3 microM), prazosin (1 microM) or glibenclamide (1 microM) did not significantly modify the biphasic responses to BK (300 nM). The biphasic responses to DA-BK were antagonized selectively by the B1 receptor antagonist des-Arg9-[Leu 8]-BK (DAL-BK) (1 microM). In contrast, the biphasic responses to BK were unaffected by DAL-BK or by several selective peptide antagonists of B2 receptors including NPC 431 (Thi5,8, D-Phe7)-BK, NPC 349 (D-Arg Hyp3,Thi5,8,D-Phe7)-BK, NPC 567 (D-Arg-Hyp3,D-Phe7)-BK and NPC 361 (D-Phe7)-BK (3 to 10 microM). These results are consistent with the view that the biphasic responses of the rat isolated stomach fundus to BK appear to be mediated by a novel BK receptor which is insensitive to blockade by B1 and B2 selective BK receptor antagonists.

Inhibitory effect of GnRH on isolated rat uterine muscle contractility.

The effect of GnRH upon uterine contractions of both non-pregnant and pregnant rats was examined in vitro. In the non-pregnant rat uterus, GnRH inhibited in a concentration-and-time dependent manner the contractions induced by acetylcholine and oxytocin, but not those caused by bradykinin and angiotensin II. GnRH also inhibited the rhythmic contractions induced by oxytocin in uterine strips from late pregnant rats. These findings show that GnRH has a direct inhibitory effect on the rat uterine contractions, suggesting that GnRH-like substances may exert modulatory influences upon rat uterine contractility.

Influence of calcium entry blockers and calmodulin inhibitors on 5-hydroxytryptamine-, potassium- and calcium-induced contractions in human umbilical artery in-vitro.

The effects of calcium (Ca2+) withdrawal, Ca2+ entry blockers and calmodulin inhibitors on the contractile responses to 5-hydroxytryptamine (5-HT), K+ and CaCl2 have been studied in human isolated umbilical artery. Following Ca2+ withdrawal from the medium (30 min), both 5-HT- and K(+)-induced contractions were virtually abolished. Ca2+ entry blockers (nifedipine, verapamil, diltiazem and cinnarizine) were significantly more effective in inhibiting 5-HT- than K(+)-induced contractions. In relation to calmodulin inhibitors, trifluoperazine inhibited all types of contractions, whereas W-7 (N-6-aminohexyl-5-chloro-1-naphthalene sulphonamide) only inhibited 5-HT- and CaCl2-induced contractions. All drugs inhibited CaCl2-induced contractions in a non-competitive manner. These findings indicate that the mechanisms by which these drugs exert their inhibitory effects on human umbilical artery are markedly different from those reported in other vascular beds.

Pharmacological profile of rat pleurisy induced by Bothrops jararaca venom.

Bothrops jararaca venom (30 micrograms/site) triggered a marked inflammatory reaction in the pleural cavity that was long-lasting and reproducible. In the first 1 h after pleurisy induction, a significant decrease of total and differential cell count was observed in comparison with control values, despite the gradual enhancement of fluid leakage. A significant increase of cell migration was observed after 3 h of pleurisy induction, due to mononuclear and neutrophil cells that peaked 8 h later and this was followed by a gradual decrease, remaining elevated up to 24 h. In parallel with cell influx, a significant increase of fluid leakage that peaked between 1 and 8 h was observed, being completely abolished after 12 h following pleurisy induction. This inflammatory response was not associated in parallel with significant changes in circulating leucocyte cells and it was significantly inhibited by compound 48/80, cyproheptadine, pyrilamine, dexamethasone, indomethacin and phenidone. Preheating of the venom (100 degrees C) caused a significant decrease of both leakage of fluid and cell migration in the pleural cavity 8 h after pleurisy induction. Previous exposure to the venom (30 micrograms/site, 5 days before) produced a significant decrease of both cell migration and fluid leakage 4 h after triggering pleurisy with the same dose of the venom. Otherwise, prior daily treatment with the venom (10 micrograms/site, 4 days) resulted only in marked fluid leakage reduction 1 h after treating the animals with BJV (30 micrograms/site). These results show that the venom elicits pro-inflammatory effects in the rat pleural cavity which involve the participation of several mediators, including histamine, 5-hydroxytryptamine and products of arachidonic pathways.

Effect of PAF-acether on the reactivity of the isolated rat myometrium.

In non-pregnant rat isolated uterine strips PAF-acether (1-100 nM) produced contractile effects on 74% of the preparations tested which were concentration-dependent in 44% of the cases (EC50 = 28 nM). All the preparations tested exhibited contractile responses to either acetylcholine or potassium. PAF-acether was less potent on myometrial strips from pregnant animals (EC50 = 0.3 microM) and was only effective on 24% of the preparations tested. A second contractile concentration-response curve was reproducible in only 14% of the preparations from non-pregnant rats (EC50 = 13 nM), whereas all strips from pregnant animals were completely refractory to a second challenge with PAF-acether. These results indicate that PAF-acether induces contraction of the isolated rat myometrium within the same range of concentrations at which it is active in other tissues.

Gossypol affects the responsiveness of isolated rat myometrium and vas deferens.

The effects of gossypol on responsiveness of both rat myometrium and vas deferens were analyzed. In myometrial strips, gossypol (1-30 microM) produced rightward displacements of the cumulative concentration-response curves to acetylcholine, bradykinin and oxytocin, accompanied by reductions in maximal responses. Gossypol (30 microM) also completely abolished the contractions induced by field stimulation of the rat vas deferens. The IC50 values for gossypol against agonist-induced myometrial contractions and field-stimulated vas deferens contractions were similar, ranging between 13 and 18 microM. These results provide additional evidence that gossypol exerts a direct and irreversible inhibition of the contractility of both male and female reproductive organs.

Tracheal responsiveness to histamine, PAF-acether and acetylcholine in normal and actively ovalbumin-sensitized guinea pigs.

The contractile effects of histamine (His), PAF-acether (PAF) and acetylcholine (Ach) were analyzed in tracheal rings from normal and ovalbumin-sensitized (OAS) guinea pigs. Although maximal responses to all agonists were enhanced in preparations from OAS guinea pigs, only the EC50 of Ach was significantly decreased. Previous treatment with 1 microM indomethacin (IND) or 10 microM quinacrine (QUIN) markedly displaced the dose-response curves for Ach on OAS preparations to the left, whereas the EC50 of His was only increased by QUIN. PAF-responses, however, were completely abolished by IND in preparations from both sensitized and unsensitized animals. These results indicate that ovalbumin sensitization significantly affects the tracheal response to Ach, His and PAF, an effect that appears to be mediated by arachidonic acid metabolites.

Propranolol and hyperthyroidism: sequential changes in serum iodothyronine (T4, T3, rT3) concentrations during therapy until clinical remission.

The sequential clinical and laboratory (serum T4, T3 and rT3 concentrations) effects of propranolol were studied in 21 hyperthyroid patients. The amount of propranolol required to achieve clinical compensation ranged from 240 to 400 mg/day. For two patients, 480 mg/day, the maximal dose used, did not produce clinical compensation. The only significant changes in serum iodothyronines was detected in the 9 patients compensated with 240 mg/day. T3 decreased from 362 to 299 ng/dl (P less than 0.05) and the rT3/T3 molar ratio increased from 3.4 to 6.5 (P less than 0.025). The increases of rT3 from 113 to 168 ng/dl and of the rT3/T4 molar ratio from 6.7 to 10.8 were not statistically significant (P = 0.052). A slight decrease of serum T3 and increase of serum rT3 occurred during the first or second week in the other patients but the changes were not sustained over the whole period of treatment. These results show that the effects of propranolol on hyperthyroidism were independent of its transitory effects on the peripheral metabolism of thyroid hormones, thus providing further support for the current view that the clinical improvement of hyperthyroid patients on propranolol therapy is probably due to beta-adrenergic receptor blockade. A small percentage of thyrotoxic patients may not show clinical improvement even when propranolol doses of more than 400 mg/day are used.

Inhibitory effect of diphenylhydantoin on myometrium from pregnant women in vitro. A comparative study with nicardipine and trifluoperazine.

In the isolated myometrium obtained from pregnant women, diphenylhydantoin inhibited both spontaneous and K(+)-evoked contractions within the same range of potency. Nicardipine was less effective in inhibiting spontaneous than K(+)-induced contractions, whereas trifluoperazine was only effective against spontaneous contractions. These results indicate that diphenylhydantoin may directly induce in vitro human myometrium relaxation by mechanisms that differ markedly from those induced by nicardipine and trifluoperazine.

Characterization of bradykinin mediating pertussis toxin-insensitive biphasic response in circular muscle of the isolated guinea pig ileum.

The mechanisms underlying the biphasic response (BR) of the circular muscle of the guinea pig ileum (CMGPI) to bradykinin (BK) have been examined. Both BK and lysyl-BK (1 nM to 1 microM) caused graded contractions followed by relaxations of the CMGPI, yielding EC50 of 21 and 92 nM for contraction and of 10 and 27 nM for relaxation, respectively. The selective B1 receptor agonist Des-Arg9-BK was without effect up to 3 microM. The potencies of BK and lysyl-BK to evoke BR were markedly increased by enalapril (3 microM) and decreased by raising the preparation tone with the thromboxane A2/prostaglandin H2-mimetic U46619 (30 ng/ml). The BR of CMGPI to BK was unaffected by atropine, yohimbine, pyrilamine, propranolol, prazosin, phorbol ester, des-Arg9-[leu8]-BK (1 microM, each), tetrodotoxin (0.3 microM), [3,4,5-trimethoxybenzoic acid-8-(diethylamino) octyl ester (10 microM), [N-6-(aminohexyl)-5-chloro-1-naphthalenosulfonamide (10 microM), glibenclamide (0.3 microM), nordihydroguaiaretic acid (50 microM), phenidone (30 microM) or dexamethasone (0.1 microM). However, indomethacin (3 microM), ibuprofen (30 microM) and 3-amino, 1-(m-[trifluoromethyl] phenyl)2-pyrazoline (10 microM) each abolished the relaxant and increased the contractile response to BK, suggesting that a cyclo-oxygenase-derived eicosanoid mediates relaxation and limits contraction. Prostaglandin (PG) E2 (up to 100 nM) caused only graded relaxations, PGF2 alpha (up to 3 microM) and 9,11-dideoxy-9 alpha,11 alpha-methanoepoxy prostaglandin F2 alpha (up to 300 ng/ml) caused only contractions and the PGI2 analog iloprost was without effect up to 1 micrograms/ml.(ABSTRACT TRUNCATED AT 250 WORDS)