Isolation of SMTP-3, 4, 5 and -6, novel analogs of staplabin, and their effects on plasminogen activation and fibrinolysis.
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Four novel triprenyl phenol metabolites, designated SMTP-3, -4, -5, and -6, have been isolated from cultures of Stachybotrys microspora IFO 30018 by solvent extraction and successive chromatographic fractionation using silica gel and silica ODS columns. A combination of spectroscopic analyses showed that SMTP-3, -4, -5, and -6 are staplabin analogs, containing a serine, a phenylalanine, a leucine or a tryptophan moiety in respective molecules in place of the N-carboxybutyl portion of the staplabin molecule. SMTP-4, -5, and -6 were active at 0.15 to 0.3 mM in enhancing urokinase-catalyzed plasminogen activation and plasminogen binding to fibrin, as well as plasminogen- and urokinase-mediated fibrinolysis. On the other hand, the concentration of staplabin required to exert such effects was 0.4 to 0.6 mM, and SMTP-3 was inactive at concentrations up to 0.45 mM. (+info)
Inhibition of endothelium-dependent hyperpolarization by endothelial prostanoids in guinea-pig coronary artery.
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1. In smooth muscle of the circumflex coronary artery of guinea-pig, acetylcholine (ACh, 10(-6) M) produced an endothelium-dependent hyperpolarization consisting of two components. An initial component that occurs in the presence of ACh and a slow component that developed after ACh had been withdrawn. Each component of the hyperpolarization was accompanied by an increase in membrane conductance. 2. Indomethacin (5 x 10(-6) M) or diclofenac (10(-6) M), both inhibitors of cyclooxygenase, abolished only the slow hyperpolarization. The initial hyperpolarization was not inhibited by diclofenac nor by nitroarginine, an inhibitor of nitric oxide synthase. 3. Both components of the ACh-induced hyperpolarization were abolished in the presence of atropine (10(-6) M) or high-K solution ([K+]0 = 29.4 mM). 4. The interval between ACh-stimulation required to generate an initial hyperpolarization of reproducible amplitude was 20 min or greater, but it was reduced to less than 5 min after inhibiting cyclooxygenase activity. Conditioning stimulation of the artery with substance P (10(-7) M) also caused a long duration (about 20 min) inhibition of the ACh-response. 5. The amplitude of the hyperpolarization generated by Y-26763, a K+-channel opener, was reproducible within 10 min after withdrawal of ACh. 6. Exogenously applied prostacyclin (PGI2) hyperpolarized the membrane and reduced membrane resistance in concentrations over 2.8 x 10(-9)M. 7. At concentrations below threshold for hyperpolarization and when no alteration of membrane resistance occurred, PGI2 inhibited the initial component of the ACh-induced hyperpolarization. 8. It is concluded that endothelial prostanoids, possibly PGI2, have an inhibitory action on the release of endothelium-derived hyperpolarizing factor. (+info)
A novel role for carbonic anhydrase: cytoplasmic pH gradient dissipation in mouse small intestinal enterocytes.
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1. The spatial and temporal distribution of intracellular H+ ions in response to activation of a proton-coupled dipeptide transporter localized at the apical pole of mouse small intestinal isolated enterocytes was investigated using intracellular carboxy-SNARF-1 fluorescence in combination with whole-cell microspectrofluorimetry or confocal microscopy. 2. In Hepes-buffered Tyrode solution, application of the dipeptide Phe-Ala (10 mM) to a single enterocyte reduced pHi locally in the apical submembranous space. After a short delay (8 s), a fall of pHi occurred more slowly at the basal pole. 3. In the presence of CO2/HCO3--buffered Tyrode solution, the apical and basal rates of acidification were not significantly different and the time delay was reduced to 1 s or less. 4. Following application of the carbonic anhydrase inhibitor acetazolamide (100 microM) in the presence of CO2/HCO3- buffer, addition of Phe-Ala once again produced a localized apical acidification that took 5 s to reach the basal pole. Basal acidification was slower than at the apical pole. 5. We conclude that acid influx due to proton-coupled dipeptide transport can lead to intracellular pH gradients and that intracellular carbonic anhydrase activity, by facilitating cytoplasmic H+ mobility, limits their magnitude and duration. (+info)
Regulation of mitochondrial KATP channel by redox agents.
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The ATP-dependent K+ channel (KATP) was purified from the inner mitochondrial membrane and reconstituted into lipid bilayer membranes. KATP activity was inhibited by high concentrations of ATP and ADP, but activated by low concentrations (up to 200 microM) of ADP. p-Diethylaminoethylbenzoate (DEB) acted as a KATP opener: at micromolar concentrations, it reversed inhibition by ATP and ADP and it also prevented KATP rundown. Pelargonidine, extracted from flowers of Pelargonium, reduced spontaneous activity of KATP channels and diminished their potentiation by DEB. Their opposite action on KATP corresponded with their opposite redox properties in reactions with free radicals: DEB behaved as an electron donor, whereas pelargonidine acted as an electron acceptor. We hypothesize that thiol groups on mitoKATP are targets for redox-active ligans. (+info)
The action of the benzopyrones on an experimental model of lymphoedema: a contribution to their mode of action.
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A number of preparations containing benzopyrones are used clinically as a therapy for lymphoedema; however, their exact mode of action is not well known. This work presents evidence which indicates that, as in the treatment of thermally induced oedemas, the benzopyrones work by enhancing the lysis of the accumulated proteins. This is evidenced by reduced levels of total protein in the extracellular compartment of the skin, while peptides and amino acids were increased in the serum at 6 and 12 h respectively after the drug's administration. Failure to observe very marked increases in peptides and amino acids at other times in the serum and skin was attributed to the rapid incorporation of these into the large number of maturing phagocytes which enter the lymphoedematous tissues. Likewise, protease activity levels were not elevated as expected. This possibly was the consequence of a number of factors including serum deactivation, inhibition of release and membrane stabilization. (+info)
The role of humic substances in drinking water in Kashin-Beck disease in China.
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We conducted in vitro and in vivo assays in a selenium-deficient system to determine if organic matter (mainly fulvic acid; FA) is involved in a free radical mechanism of action for Kashin-Beck disease. Cartilage cell culture experiments indicated that the oxy or hydroxy functional groups in FA may interfere with the cell membrane and result in enhancement of lipid peroxidation. Experiments with rats demonstrated that toxicity from FA was reduced when the hydroxy group was blocked. Induction of lipid peroxidation by FA in liver and blood of rats was similar to that exhibited by acetyl phenyl hydrazine. FA accumulated in bone and cartilage, where selenium rarely concentrates. In addition, selenium supplementation in rats' drinking water inhibited the generation of oxy-free radicals in bone. We hypothesized that FA in drinking water is an etiological factor of Kashin-Beck disease and that the mechanism of action involves the oxy and hydroxy groups in FA for the generation of free radicals. Selenium was confirmed to be a preventive factor for Kashin-Beck disease. (+info)
Disposition and metabolism of 2-(2''(1'',3''-dioxolan-2-yl)-2- methyl-4-(2'-oxopyrrolidin-1-Yl)-6-nitro-2h-1-benzopyran (SKP-450) in rats.
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The disposition and metabolism of the new antihypertensive agent 2-(2"(1", 3"-dioxolan-2-yl)-2-methyl-4-(2'-oxopyrrolidin-1-yl)-6-nitro -2H-1-benzopyran (SKP-450) were investigated in male rats after single oral and i.v. doses of 14C-labeled compound. After an oral 2.0 mg/kg dose, mean radiocarbon recovery was 98.2 +/- 2.3% with 31.1 +/- 7.3% in the feces and 67.1 +/- 14.3% in the urine. Biliary excretion of radioactivity for the first 24-h period was approximately 40%, suggesting that SKP-450 is cleared either by hepatobiliary excretion or by renal excretion. SKP-450 was well absorbed; bioavailability calculated on the basis of radioactivity was 68 to 97%. Tissue distribution of the radioactivity was widespread with high concentrations in the liver and kidney but low central nervous system penetration. Radio-HPLC analysis of bile and urine from rats indicated the extensive metabolism of SKP-450 into oxidative metabolites. Oxidative metabolism of the dioxolanyl ring resulted in an aldehyde intermediate, subsequently confirmed in vitro, which was further oxidized to the corresponding carboxylic acid (M1) or reduced to the corresponding alcohol (M3). No parent drug was detected in the urine or bile. Glucuronide conjugate of M3 was also detected in urine and bile, accounting for 5.8 +/- 2.1 and 8.9 +/- 3. 7% of the excreted radioactivity, respectively. Quantitative data obtained from plasma samples suggest that the majority of circulating radioactivity was associated with metabolites. Our results suggest that the long duration of pharmacological activity of SKP-450 (>10 h) is largely attributable to its metabolites. (+info)
Pharmacokinetic profile of alniditan nasal spray during and outside migraine attacks.
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AIMS: To compare the pharmacokinetic profile of intranasal alniditan during and outside migraine attacks, and to investigate the relationship between initial rise of alniditan plasma concentration, and headache improvement. METHODS: Twenty-seven migraine patients (age: 18-65 years) were randomized to receive alniditan 2 mg or 4 mg, and investigated both during and outside a migraine attack. Maximal plasma concentrations (Cmax), time to Cmax (tmax), and the area under the curve over 2 h (AUC(0,2 h)), were calculated from the individual plasma concentration-time profile, obtained from 10 blood samples in each patient, during each of the two administrations. RESULTS: Alniditan was rapidly absorbed into the systemic circulation (tmax=11 min). All investigated pharmacokinetic parameters (Cmax, tmax, AUC(0,2 h)) were similar during and outside migraine attacks, both in the 2 mg (n = 13) and the 4 mg group (n = 14). In the 4 mg group, during attacks, mean plasma alniditan concentration at 5 min after administration (Ct=5) in responders (21+/-16 ng ml(-1); n=10) was significantly higher than the Ct=5 in nonresponders (3+/-3 ng ml(-1); P=0.01; n=4). However, the Cmax and AUC(0,2 h) in responders (33+/-18 ng ml(-1) and 12+/-6 ng ml(-1) h) were also significantly higher than the Cmax and AUC(0,2 h) in nonresponders (13+/-9 ng ml(-1); P=0.048 and 5+/-3 ng ml(-1) h; P=0.03). CONCLUSIONS: Absorption of alniditan nasal spray was not affected by migraine attacks, although 95% confidence intervals were wide. Early rise of plasma concentrations and the amount of drug in the circulation were related to headache improvement in the higher dose group. (+info)