Effects of oblongine chloride,an alkaloid from Leontice leontopetalum on guinea-pig isolated smooth muscle and heart

1. The effects of (−)oblongine chloride, a quaternary alkaloid from Leontice leontopetalum, on guinea-pig isolated ileal longitudinal segments, main pulmonary artery rings, spontaneously-beating atrium and isolated perfused heart were studied.2. Oblongine chloride (3 × 10⁻⁵−10⁻³ M) caused concentration-dependent relaxation of ileum, an effect which was not blocked by propranolol (10⁻⁶ M) alone or in combination with prazosin (3 × 10⁻⁸ M), or by indomethacin (10⁻⁶ M), but was reduced by desensitization of the preparation by prior exposure to 3 × 10⁻⁵ M ATP and, at high concentrations of oblongine, by a combination of propranolol and yohimbine (3 × 10⁻⁶ M).3. Oblongine chloride (10⁻⁵−3 × 10⁻³ M) caused concentration-dependent relaxation of epinephrine-precontracted pulmonary artery. This effect was not affected by propranolol or by indomethacin but was significantly attenuated by pretreatment with 3 × 10⁻⁵ M ATP and potentiated by pretreatment with quinacrine (10⁻⁵ M).4. Oblongine chloride (10⁻⁵M−3 × 10⁻³ M) caused concentration-dependent increase in the contractility but did not affect the rate of the atrium. Similar effects were obtained with isolated perfused heart except that large concentrations of oblongine (10⁻³, 3 × 10⁻³ M) inhibited both contractility and rate of the heart. The inotropic effects of oblongine on the atrium were not blocked by propranolol or indomethacin but were significantly blocked by quinacrine.5. These observations suggest that the effects of oblongine chloride are not mediated by the stimulation of adrenergic receptors on these preparations but are mediated by purinergic receptors and by an interference with the arachidonic acid metabolism but not along the cyclooxygenase pathway.     

Metabolism of bisphenol A in isolated rat hepatocytes and oestrogenic activity of a hydroxylated metabolite in MCF-7 human breast cancer cells

1. The metabolites of bisphenol A (BPA; 2,2-bis(4-hydroxyphenyl)propane) in freshly isolated rat hepatocytes and the oestrogenic activities of BPA and its metabolites, particularly 3-hydroxybisphenol A (3-OH-BPA), in MCF-7 cells and competitive binding assays have been studied, respectively. 2. During a 2-h incubation, almost all of the BPA (0.25mM) added to the hepatocyte suspensions was rapidly converted to a major conjugate, monoglucuronide (approximately 75% of total metabolites), and two minor conjugates, which were tentatively identified as monosulphates of BPA and a hydroxylated intermediate, 3-OH-BPA, as determined by mass spectroscopy coupled with HPLC or GC/MS. On the other hand, free 3-OH-BPA was identified as a trace metabolite, whose level was approximately 1 or 2 μM at 1?h in hepatocyte suspensions treated with 0.25 or 0.5mM BPA, respectively. 3. In another experiment, 3-OH-BPA as well as BPA displaced competitively17β-oestradiol bound to the recombinant human oestrogen receptor α in a concentration dependent-manner: IC₅₀ of diethylstilbestrol, BPA and 3-OH-BPA were approximately 2.5 × 10^?8, 10^?5 and 5 × 10^?8 M, respectively. Further, BPA and 3-OH-BPA at intermediate concentrations (10^?7-10^?6 M) caused proliferation of MCF-7 human breast cancer cells, whereas the effect of BPA was more potent than that of 3-OH-BPA. At higher concentrations, both BPA (> 10^?4 M) and 3-OH-BPA (> 10^?5 M) were cytotoxic. 4. Based on the proliferative potency in MCF-7 cells and the IC₅₀ for the competitive binding, the oestrogenic activity of 3-OH-BPA was less than that of BPA. These results indicate that BPA itself rather than its metabolite acts as a xeno-oestrogen and that 3-OHBPA is cytotoxic, possibly acting via reactive semiquinone and/or quinone metabolites, rather than a xeno-oestrogenic mechanism, in MCF-7 cells.     

Characterization of muscarinic receptors on the isolated guinea pig ileum at pharmacologically low concentrations

• 1.1. Several selective and non-selective muscarinic agonists (McN-A-343, RS-86, arecoline, oxotremorine-M, pilocarpine, cis-dioxolane, and acetylcholine) were examined for relaxant activity in the isolated guinea-pig ileum at pharmacologically low concentrations.
• 2.2. The concentrations studied include: 1 × 10⁻¹²M, 3 × 10⁻¹²M, 1 × 10⁻¹¹M, 3 × 10⁻¹¹M and 1 × 10⁻¹⁰M.
• 3.3. None of the compounds exhibited relaxant activity in both the field and non-field stimulated ileum.
• 4.4. All of the above compounds exert muscarinic agonist activity in a concentration range of 1 × 10⁻⁹M to 1 × 10⁻⁶M (Williams et al., 1992).
• 5.5. Thus, in the isolated guinea-pig ileum, muscarinic agonists do not exert relaxant activity of the gastrointestinal tract at low concentrations.

     

乙酰唑胺对表达水孔蛋白1的非洲爪蟾卵母细胞转运水功能的影响

目的观察乙酰唑胺对水孔蛋白1(AQP1)水转运功能的影响。方法将AQP1 cRNA 10 ng注射入非洲爪蟾卵母细胞,观察并记录给予1×10^-7～1×10^-5 mol·L^-1乙酰唑胺后卵母细胞在低渗溶液中的膨胀率,并计算其渗透水通透性(Pf)的变化。结果非洲爪蟾卵母细胞表达AQP1蛋白后,在低渗溶液中迅速膨胀,Pf值显著增加至1.82×10^-2 cm·s^-1,而注射水的阴性对照仅为0.25×10^-2 cm·s^-1。AQP抑制剂HgCl₂使Pf值降至0.64×10^-2 cm·s^-1;1×10^-7～1×10^-5 mol·L^-1乙酰唑胺处理后,Pf值分别降至1.43,1.24和0.93×10^-2 cm·s^-1。结论乙酰唑胺剂量依赖性地降低AQP1介导的渗透水通透性,抑制AQP1转运水的功能。     

地塞米松对人眼小梁细胞水通道蛋白-1表达的影响

目的 :观察地塞米松对人眼小梁细胞水通道蛋白 -1(AQP -1)表达的影响。方法 :通过RT -PCR方法 ,半定量检测原代培养的人眼小梁细胞AQP -1的mRNA水平及不同浓度地塞米松的作用。结果 :正常人眼小梁细胞AQP -1的mRNA(灰度比 )为1 643±0 354,10-8mol、5×10-8mol、10-7mol、5×10-7mol地塞米松作用3d为1 577±0 405、1 117±0 443、0 458±0 301、0 267±0 243。地塞米松浓度≥5×10 -8mol出现抑制作用 (P<0 05)。结论 :地塞米松使培养的正常人眼小梁细胞AQP -1的mRNA减少 ,可能是皮质类固醇性青光眼房水流出阻力增加的原因之一。     

Cytotoxicity and immunotoxicity of cyclopiazonic acid on human cells

In this study, in vitro cytotoxicity and immunotoxicity of the mycotoxin cyclopiazonic acid (CPA) was evaluated on human cells. To evaluate cytoxicity, several cellular targets were used (CD34+, monocytes, THP-1 and Caco-2). Monocytes were more sensitive to CPA than the THP-1 monocytic cell line after 48 h of incubation in the tested conditions. Half maximal inhibitory concentration (IC50) were determined to be 8.5 × 10⁻⁸ and 1.75 × 10⁻⁷ M for monocytes and THP1, respectively, while IC50 > 1.25 × 10⁻⁷ M was observed for Caco-2 and CD34+ cells. The CPA effect on macrophage differentiation was also examined at non-cytotoxic concentrations. The monocyte differentiation process was markedly disturbed in the presence of CPA. After 6 days of culture, CD71 expression was downregulated, while CD14 and CD11a expressions did not change. Moreover, activated macrophages showed a raised burst activity and TNF-α secretion. Overall, the results indicated that CPA exhibited toxicity on various human cellular models. Moreover, at non-cytotoxic concentrations, CPA disturbed human monocytes differentiation into macrophages. This work contributes to understanding the immunosuppressive properties of this food-related toxin.     

Lymphokines production by concanavalin A-stimulated mouse splenocytes: modulation by Met-enkephalin and a related peptide

Methionine-enkephalin (ME) and its synthetic congener Tyr-D-Ala-Gly-Me-Phe-Gly-NH.C₃H₇-iso (82/205), in a concentration-dependent biphasic manner modulated the concanavalin A (Con A)-stimulated phagocytosis-promoting (PP)-activity elaboration in the culture supernatants of mouse splenocytes in vitro. Both these peptides at 1 × 10⁻⁵ and 1 × 10⁻⁶ M inhibited the production of PP activity; conversely, at 1 × 10⁻⁷−1 × 10⁻⁹ M they augmented it. Peptide 82/205 was nearly 1.2-fold more inhibitory and approximately 1.8-fold more potent in augmenting the PP activity elaboration. The PP activity appeared to be due to lymphokines (LK) gamma interferon and interleukin-4 as the neutralizing concentrations of monoclonal antibodies against these LK significantly (p<0.05) inhibited it. Cycloheximide (50.0 μg/ml) completely inhibited the production of LK indicating their de novo synthesis. The peptides appeared to exert their inhibitory and augmenting effects via δ-and μ-opioid receptors, respectively, as pretreatment of splenocytes with 100-fold higher (1 × 10⁻³ M) concentration of naloxone was required to block their inhibitory effect; the augmenting effect was blocked by 1 × 10⁻⁵ M only. None of the peptides or naloxone could directly stimulate the splenocytes for PP-LK elaboration.     

Characterization of 5-Hydroxytryptamine receptors in goat cerebral arteries

• 1.1. In isolated goat middle cerebral artery segments, 5-hydroxytryptamine (5-HT, 10⁻⁸-3 × 10⁻⁵ M) elicited concentration-dependent contractions with EC₅₀ = 2.1 (1.9−2.5) × 10⁻⁷ M and E_max = 64 ± 2% of 50 mM KCl-induced contraction.
• 2.2. Several 5-HT receptor agonists were used: (a) the agonist of 5-HT₂ receptors α-methyl-5-hydroxytryptamine (10⁻⁷ -3 × 10⁻⁴ M) induced strong contraction (51± 6%); (b) the selective agonists of 5-HT_1A receptors sumatriptan (10⁻⁸ - 10⁻⁵ M) and 5-carboxamidotryptamine (10⁻⁹ - 10⁻⁴ M) and the agonist of 5-HT_1A receptors 8-hydroxy-2-(di-n-propylamino)tetralin (10⁻⁷ - 3 × 10⁻⁵ M) induced weak contractions (8, 18 and 14%, respectively); and (c) the agonist of 5HT₃ receptors 2-methyl-5-hydroxytryptamine (3 × 10⁻⁶ - 10⁻⁴ M) induced almost negligible contraction.
• 3.3. Pretreatment with the antagonist of 5-HT_1A and 5-HT_1B receptors cyanopindolol (10⁻⁸, 10⁻⁶ M), the antagonist of 5-HT₁/5-HT₂ receptors methysergide (10⁻¹¹, 10⁻⁹ M) and the antagonist of 5-HT₂ receptors ketanserin (10⁻¹¹, 10⁻⁹ M) induced non-competitive inhibition of the concentration-response curve to 5-HT. The antagonist of 5-HT₃ receptors 3-trophanyl-3,5-dichlorobenzoate (10⁻⁷, 10⁻⁵ M) did not inhibit the contractile curve to 5-HT.
• 4.4. These results suggest that 5-HT contracts the goat middle cerebral artery by acting mainly on 5-HT₂ receptors.

     

Progesterone and pregnanolone derivatives relaxing effect on smooth muscle

• 1.1. The effect of gestagens, 5α-hydroxyprogesterone (10⁻⁶−6 × 10⁻⁵ M), 5β-hydroxyprogesterone (10⁻⁶−3 × 10⁻⁵ M), progesterone (6 × 10⁻⁶−10⁻⁴ M), pregnanolone (10⁻⁶−10⁻⁵ M), allopregnanolone (10⁻⁶−10⁻⁴ M) and epipregnanolone (10⁻⁶−6 × 10⁻⁵ M) on rat uterine contractions induced by KCl (60 mM), has been assayed.
• 2.2. All drugs assayed relaxed the tonic-contraction induced by KCl in a concentration-dependent way. The respectives IC₅₀ were 31.3 ± 4.1 × 10⁻⁶ M (progesterone), 8.9 ± 0.8 × 10⁻⁶ M (5α-hydroxyprogesterone 3.8 ± 0.3 × 10⁻⁶ M (5β-hydroxyprogesterone), 3.1 ± 0.1 × 10⁻⁶ M (pregnanolone), 21.2 ± 3.1 × 10⁻⁶ M (allopregnanolone) and 6.3 ± 1.3 × 10⁻⁶ M (epipregnanolone). This relaxing effect was partially or totally counteracted by CaCl₂ (1–10 mM)
• 3.3. Cycloheximide (10 μg/ml) significantly shifted to the right the effect of allopregnanolone but not the effect of the other drugs. Actinomycin D (5 μg/ml) did not modify the effect of allopregnanolone.
• 4.4. Our results suggest that the relaxing effect of gestagens in the rat uterus could be related to inhibition on calcium influx and mainly occur through non-genomic mechanisms.

     

Effects of cirsiliol,a flavone isolated from Achillea fragrantissima,on rat isolated ileum

• 1.1. In concentrations from 10⁻⁸ M to 3 × 10⁻⁴ M, cirsiliol caused concentration-dependent relaxation of rat isolated ileum.
• 2.2. Phentolamine (10⁻⁶ M) or phentolamine and propranolol (10⁻⁶ M) had no significant effects on the concentration-effect curves or on the EC₅₀ of cirsiliol on the ileum.
• 3.3. Cirsiliol shifted to the right the acetylcholine (Ach) concentration-effect curves on ileum and significantly inhibited the maximum contractions induced by Ach.
• 4.4. In Ca²⁺-free, depolarizing solution, cirsiliol shifted to the right the CaCl₂ concentration-effect curves and inhibited the maximum contractions induced by CaCl₂ on ileum.
• 5.5. Large concentrations (10⁻⁴ M, 3 × 10⁻⁴ M) of cirsiliol induced relaxation followed by contraction of the ileal segments incubated in Ca²⁺-free solution.
• 6.6. In Ca²⁺-free solution, cirsiliol (10⁻⁴ M, 3 × 10⁻⁴ M) caused concentration-dependent potentiation of the ileal contractions induced by 3 × 10⁻³ M Ach when the latter was added 2–3 min after cirsiliol. When Ach was added 15–20 min after cirsiliol, the latter compound inhibited the Ach-induced contractions.
• 7.7. These observations suggest that cirsiliol inhibits Ca²⁺ influx but stimulates Ca²⁺ release from intracellular stores. Furthermore, they suggest that cirsiliol utilizes the same Ca²⁺ source used by acetylcholine in Ca²⁺-free solution.

     

Error structure for the HPLC analysis for atenolol,metoprolol and propranolol: a useful weighting method in parameter estimation

Three reversed-phase high performance liquid chromatography (HPLC) methods with UV detection were developed and fully validated for the quantification of three β-blockers: atenolol, metoprolol and propranolol. After validation, error structures for the HPLC analysis were established using a convenient and practical procedure. The mean percentage of relative standard deviation (RSD) of the experimental concentrations (C), were less than 4.29% for proportionality and less than 3.68% for precision for any of the drugs, which allowed the quantitation of β-blockers assayed at concentrations in the range 25–0.78 μg·ml⁻¹. The error structures for the HPLC analysis were: SD (μg·ml⁻¹)=5.02×10⁻²+0.65×10⁻² C for atenolol, SD (μg·ml⁻¹)=4.55×10⁻²+0.63×10⁻² C−7.58×10⁻⁶ C³ for metoprolol and SD (μg·ml⁻¹)=2.73×10⁻²+1.46×10⁻² C−3.49×10⁻⁴ C² for propranolol. The reciprocal of the square of the SD of the drug concentrations measured within the calibration curve could be used as weighting methods in parameter estimation by non-linear regression.     

Influence of hormonal status in relaxant effect of diethylstilbestrol and nifedipine on isolated rat uterus contraction

• 1.1. The effects of diethylstilbestrol (DES, 10⁻⁷-10⁻⁵ M) and nifedipine (10⁻¹⁰-10⁻⁷ M) on KCl (60 mM)-induced tonic contraction in the uterus of ovariectomized and 17β-estradiol (0.1 mg/kg/day, s.c.)-, 17α-estradiol (0.1 mg/kg/day, s.c.)-, or progesterone (2 mg/kg/day, s.c.)-treated rats have been assayed.
• 2.2. The dose-dependent relaxation produced by nifedipine in ovariectomized rats (EC₅₀ = 5.59 ± 1.25 × 10⁻⁹ M) is potentiated in uterus of rats treated with 17β-estradiol and progesterone (EC₅₀ = 0.59 ± 0.1 and 0.49 ± 0.1 × 10⁻⁹ M, respectively) but not in the 17α-estradiol-treated rats (3.01 ± 0.6 × 10⁻⁹ M).
• 3.3. The relaxation produced by DES on ovariectomized rats (EC₅₀ = 0.84 ± 0.14 × 10⁻⁶ M) is reduced when the rats are treated with 17β-estradiol (EC₅₀ = 2.22 ± 0.2 × 10⁻⁶ M) or progesterone (EC₅₀ = 1.24 ± 0.08 × 10⁻⁶ M), but unmodified by 17α-estradiol (EC₅₀ = 0.58 ± 0.01 × 10⁻⁶ M).
• 4.4. The nifedipine-induced relaxation is reversed with Bay K 8644 (10⁻¹⁰-10⁻⁶ M) in all experimental conditions. However, Bay K 8644 counteracted the relaxation of DES at 45.7% on ovariectomized rats but this was lower than 30% in the other groups.
• 5.5. Our results suggest that in ovariectomized rats the effects of both nifedipine and DES are similar, but 17β-estradiol and progesterone produce a contrary effect on the relaxation induced by nifedipine and DES (by increasing the nifedipine and decreasing the DES effects).
• 6.6. The modifications produced by 17α-estradiol are similar to those produced by the ovariectomy and this suggests that 17α-estradiol is a drug lacking estrogenic activity.

     

Effects of Ro 5-4864 and PK 11195 in rat duodenum and vas deferens

Ro 5-4864 and PK 11195 inhibit in a concentration-dependent manner carbachol-induced contractions in rat duodenum (IC₅₀: 1.56 ± 0.07 × 10⁻⁵ M and 1.18 ± 0.07 × 10⁻⁵ M respectively). The antagonism is non-competitive and is not mediated by peripheral-type benzodiazepine receptors. The Ro 5-4864 effect is modulated by the calcium concentration of the Tyrode-Ringer solution. In the presence of 1 mM NaF/10 μM AlCl₃, Ro 5-4864 and PK 11195 do not inhibit carbachol-induced contractions. Moreover, Ro 5-4864 and PK 11195 significantly relax AlF₄⁻-induced contractions, with IC₅₀ values of 2.01±0.12×10⁻⁵ M and 1.28 ± 0.11 × 10⁻⁵ M respectively. This effect is also modulated by the calcium concentration of the medium. Pertussis toxin potentiates the antagonist effects of Ro 5-4864 and PK 11195 on carbachol-induced contractions, but cholera toxin does not affect them. Ro 5-4864 and PK 11195 inhibit ⁴⁵Ca²⁺ uptake induced by KCl (120 mM) in rat vas deferens, but do not affect either basal ⁴⁵Ca efflux or noradrenaline-induced ⁴⁵Ca²⁺ efflux. Only high doses of PK 11195 (above 5 × 10⁻⁵ M) are able to produce a slight reduction of the accumulation of inositol phosphates induced by methoxamine in rat vas deferens, while Ro 5-4864 has no significant effect. Finally, Ro 5-4864 and PK 11195 reduce calcium influx, but do not seen to be the only mechanism of the antagonistic effect on carbachol-induced contractions. An alteration of other second messengers. probably cyclic monophosphate nucleotides, may be involved.     

Using ovarian and brain cell culture from the Mullet,Liza klunzingeri,to assess the inhibitory effects of benzo[a]pyrene on aromatase activity

We assessed the toxic effects of benzo[a]pyrene (BaP) on cell viability, aromatase (Aro) activity and steroid production using ovarian and brain cell cultures obtained from Mullet, Liza klunzingeri. The brain and ovary were minced and digested, and the cells were suspended in Leibovitz's L-15 medium supplemented with 15% and 20% fetal bovine serum. The cell suspensions were seeded on 25-cm² cell-culture flasks at 1 × 10⁶ cells/mL and incubated at 25 °C for 2 weeks. A BaP concentration of 10⁻⁵ mol/L was accepted as the half-maximal inhibitory concentration. Ovarian and brain cells were exposed to different concentrations of BaP [0 (control), 10⁻⁶, 2 × 10⁻⁶, 3 × 10⁻⁶ mol/L] and incubated at 30 °C. At different sampling times (0, 12, 24 and 48 h) 40 ng/10⁵ cells of 1,4,6-androstatriene-3,17-dione (ATD) was added to each well. Aro activity, 17β-estradiol (E2) and ATD production were determined. The sensitivity of the cultivated ovarian and brain cells to BaP increased dose dependently. BaP was a potent inhibitor of Aro activity at 2 × 10⁻⁶ and 3 × 10⁻⁶ mol/L, both in the cultivated brain and ovarian cells at different sampling times, with 10⁻⁶ mol/L BaP found to be the least potent Aro inhibitor. E2 production decreased from cultivated ovarian and brain cells treated by different concentrations of BaP. In conclusion, BaP is able to change the activity of Aro and disrupt the biosynthesis of estrogens, and thus affects reproduction in fish.     

Enhancement by captopril of bradykinin-induced calcium transients in cultured endothelial cells of the bovine aorta

Using microscopic fluorometry and fura-2-loaded cultured bovine aortic endothelial cells, we determined the effects of captopril, an angiotensin converting enzyme (ACE) inhibitor, on bradykinin-induced Ca²⁺ transients in endothelial cells. In the presence of extracellular Ca²⁺, 10⁻⁹ M bradykinin induced an early rise in the transients followed by sustained elevations of cytosolic calcium concentration ([Ca²⁺]_i). Bradykinin concentration-dependently increased [Ca²⁺]_i (EC₅₀ 6.7 × 10⁻⁹ M). Captopril, 10⁻⁵ M, enhanced and prolonged the bradykinin-induced Ca²⁺ transients and shifted the concentration-response curve to the left (EC₅₀ 8.5 × 10⁻¹⁰ M). In porcine coronary aterial strips with intact endothelium, cumulative applications of bradykinin induced an endothelium-dependent relaxation during prostaglandin F_2α-induced contraction (EC₅₀ = 2.0 × 10⁻⁹ M). Treatment with 10⁻⁵ M captopril enhanced the bradykinin-induced relaxation and shifted the concentration-response curve to the left (EC₅₀ = 7.6 × 10⁻¹⁰ M). Thus, captopril enhances the bradykinin-induced relaxation by mechanisms mainly dependent on the endothelium, namely the inhibition of ACE.     

Flow-injection fluorimetric determination of penicillamine and tiopronin in pharmaceutical preparations

Two flow-injection methods for the fluorimetric determination of penicillamine and tiopronin are proposed. The procedures are based on the oxidation of these drugs by thallium(III). In hydrochloric acid medium the fluorescence of thallium(I) formed in the oxidation of penicillamine or tiopronin is monitored using excitation and emission wavelengths of λ_ex = 227 nm and λ_em = 419 nm respectively. Linear calibration graphs were obtained between 3 × 10⁻⁷ and 8 × 10⁻⁶ M for penicillamine and between 8 × 10⁻⁷ and 2 × 10⁻⁵ M for tiopronin with sampling frequencies of 90 and 45 samples h⁻¹ respectively. The relative standard deviations were in the ranges 0.48-0.29% for penicillamine and 1.04-0.31% for tiopronin. The applicability of the method to the determination of both drugs in pharmaceutical preparations was demonstrated by investigating the effect of potential interferences and by analysis of commercial preparations.     

Effect of naringin and naringenin on contractions induced by noradrenaline in rat vas deferens—I. Evidence for postsynaptic alpha-2 adrenergic receptor

• 1.1. Naringin at all doses (2 × 10⁻⁶, 5 × 10⁻⁷, and 1 × 10⁻⁷ M) significantly increased contractions induced by noradrenaline in rat vas deferens but the increments of maximal contraction were not concentration-dependent.
• 2.2. In a medium containing 1 × 10⁻⁶ M yohimbine (a selective blocker of α₂-adrenoceptor) and naringin, the curve constructed with noradrenaline decreased below the control curve.
• 3.3. Naringenin (aglycone of naringin) (2 × 10⁻⁶ and 1 × 10⁻⁷ M) increased the contractile effect of noradrenaline and the maximal effect evoked was related to the maximal dose of naringenin.
• 4.4. The α₂ antagonism produced by yohimbine in the naringenin-noradrenaline association were retained at two doses of naringenin tested and we noticed a similar behaviour when we used clonidine-noradrenaline.

     

The effects of veratridine and BDF 9148 on the action potentials and contractility of the rat right ventricle

• 1.1. The effects of veratridine, BDF 9148 and lignocaine on the action potentials and contractile force of the electrically-driven rat right ventricle have been determined.
• 2.2. Veratridine at 10⁻⁷-10⁻⁶M and BDF 9148 at 10⁻⁷-10⁻⁵M had no effect on the threshold potential or amplitude but prolonged the ventricular action potentials.
• 3.3. In contractility studies, veratridine at 10⁻⁷-10⁻⁶M augmented the cardiac stimulation responses and the augmenting effects with 3 × 10⁻⁷ and 10⁻⁶ M were greater at 2 than 4 Hz. In the presence of veratridine at 3 × 10⁻⁶M, the ventricle would not pace.
• 4.4. BDF 9148 at 10⁻⁷-10⁻⁵M augmented the cardiac stimulation responses and the augmenting effects with 10⁻⁷ and 3 × 10⁻⁷M were greater at 2 than 4 Hz, and the effect was maximal at 3 × 10⁻⁷M and submaximal at 10⁻⁵ M. The effects of BDF 9148 at 10⁻⁵ were not readily reversible.
• 5.5. Lignocaine at 10⁻⁴ M had no effect on the ventricular action potential duration but decreased the threshold potential and amplitude and also reduced the cardiac stimulation force responses. In the presence of lignocaine, the augmenting effects of veratridine and BDF 9148 on ventricular force were reduced.
• 6.6. In summary this study has shown that BDF 9148 prolongs the action potential and augments the contractile force responses of the rat right ventricle by a lignocaine-sensitive mechanism. BDF 9148 or similar drugs may have potential as positive inotropes in the treatment of heart failure.

     

Acidic hydrolysis of bromazepam studied by high performance liquid chromatography. Isolation and identification of its degradation products

A kinetic study on the acidic hydrolysis of bromazepam was carried out in 0.01 M hydrochloric acid solution at 25 and 95°C. A reversed-phase HPLC method was developed and validated for the determination of bromazepam and its degradation products. Bromazepam degraded by a consecutive reaction with a reversible first step. Two degradation products were isolated and identified by infrared, ¹H and ¹³C nuclear magnetic resonance and mass spectroscopy. Spectroscopic data indicated that N-(4-bromo-2-(2-pyridylcarbonyl)phenyl)-2-aminoacetamide was the intermediate degradation product of this acid hydrolysis, whereas 2-amino-5-bromophenyl-2-pyridylmethanone was the final one. Therefore, the mechanism of this acid-catalysed hydrolysis involved initial cleavage of the 4,5-azomethine bond, followed by slow breakage of the 1,2-amide bond. Statistical evaluation of the HPLC method revealed its good linearity and reproducibility. Detection limits were 3.8×10⁻⁷ M for bromazepam, 6.25×10⁻⁷ M for the intermediate and 8.16×10⁻⁷ M for the benzophenone derivative.     

Effects of perhexiline on contractile response of rabbit aorta to norepinephrine and potassium

Perhexiline (3.2 × 10^?7 -6.4 × 10^?6 M) and verapamil (2 × 10^?8 -2 × 10^?7 M) inhibited the contraction of rabbit aorta induced with 40 mM K⁺ and with low concentrations (5.9 × 10^?9 -5.9 × 10^?8 M) of norepinephrine more effectively than the contraction induced by higher concentrations of norepinephrine. The tension induced by 1.2 × 10^? M norepinephrine was augmented with the above concentrations of perhexiline and verapamil. Higher concentrations (3.2 × 10^?5 -6.4 × 10^?5 M) of perhexiline significantly reduced the peak tension induced by norepinephrine. The results suggest that perhexiline is a Ca²⁺ antagonist and also has an unspecific spasmolytic action.