Effect of chito-oligosaccharide on the intestinal absorptions of phenylethanoid glycosides in Fructus Forsythiae extract

Phenylethanoid glycosides, the main active ingredients in Fructus Forsythiae extract possesses strong antibacterial, antioxidant and antiviral effects, and their contents were higher largely than that of other ingredients such as lignans and flavones, but their absolute bioavailability orally was significantly low, which influenced clinical efficacies of its oral preparations seriously. In the present study, the absorption mechanism of phenylethanoid glycosides was studied using in vitro Caco-2 cell model. And the effect of chito-oligosaccharide (COS) on the intestinal absorption of phenylethanoid glycosides in Fructus Forsythiae extract was investigated using in vitro, in situ and in vivo models. The pharmacological effects such as antiviral activity improvement by COS were verified by MDCK cell damage inhibition rate after influenza virus propagation. The observations from in vitro Caco-2 cell showed that the absorption of phenylethanoid glycosides in Fructus Forsythiae extract so with that in monomers was mainly restricted by the tight junctions, and influenced by efflux transporters (P-gp and MRP2). Meanwhile, the absorption of phenylethanoid glycosides in Fructus Forsythiae extract could be improved by COS. Besides, COS at the same low, medium and high concentrations caused a significant, concentration-dependent increase in the P_app-value for phenylethanoid glycosides compared to the control group (p < 0.05), and was all safe for the Caco-2 cells. The observations from single-pass intestinal perfusion in situ model showed that the intestinal absorption of phenylethanoid glycosides can be enhanced by COS. Meanwhile, the absorption enhancing effect of phenylethanoid glycosides might be saturable in different intestine sites. In pharmacokinetics study, COS at dosage of 25 mg/kg improved the bioavailability of phenylethanoid glycosides in Fructus Forsythiae extract to the greatest extent, and was safe for gastrointestine from morphological observation. In addition, treatment with Fructus Forsythiae extract with COS at dosage of 25 mg/kg prevented MDCK cell damage upon influenza virus propagation better than that of control. All findings above suggested that COS at dosage of 25 mg/kg might be safe and effective absorption enhancer for improving the bioavailability of phenylethanoid glycosides and the antiviral activity in vitro in Fructus Forsythiae extract.     

An unrecorded species in Korea:Monochasma sheareri (S. Moore) maxim, ex Franch. Et Sav. (Scrophulariaceae)

Plants of a genus and species previously unrecorded in Korea were collected from the hillside along a forest road at the Gwaneum peak in the Byeonsanbando National Park, Buan-gun, Jeollabuk-do, together with plants belonging to Gramineae and Cyperaceae.Monochasma sheareri (S. Moore) Maxim, ex Franch. et Sav. (Scrophulariaceae) is most similar toM. savatieri Franch. ex Maxim., but differs distinctively in several morphological characters. WhereasM. sheareri exhibits a slender stem, and a calyx that is longer than the corolla, plants ofM. savatieri, which is distributed in Japan and China, have stout stems with glandular pilose trichomes, along with calyxes that are shorter than their corollas. In addition, seeds ofM. sheareri are elliptical, with falcate trichomes on their surfaces. This new plant has been given a Korean name, “Byeon-san-but-sal-i-pul”, based on its parasitic habit and features of its natural habitat. Here, we describe its morphological characters and provide a taxonomic key and illustrations, plus photographs of the flower, fruit, and roots.     

Adventitious Shoot Induction from Internode and Root Explants in a Semiparasitic Herb Monochasma savatieri Franch ex Maxim

A highly efficient protocol for the induction of adventitious shoots from young internode and root explants of a semiparasitic medicinal herb Monochasma savatieri Franch ex Maxim was developed. MS basal medium supplemented with 5 µM thidiazuron (TDZ) induced 32 adventitious shoots/explant, which was double the number obtained using the same concentration of 6-benzyladenine (BA). Hyperhydric shoots were observed when 10 µM of any cytokinin was added to MS media. Use of any cytokinin at 2.5 µM produced an average of 14–21 adventitious shoots/root explant. Shoots formed roots in vitro more effectively than α-naphthaleneacetic acid when indole-3-butyric acid and indole-3-acetic acid were used at 1.0 µM. Two-month-old rooted plantlets were transplanted to vermiculite and 70% survived after 4 months.

     

Tyrosinase Inhibitors from the Aerial Parts of Wulfenia carinthiaca Jacq.

Activity guided isolation of a MeOH extract of the aerial plant parts of Wulfenia carinthiaca Jacq . (Plantaginaceae), using a mushroom tyrosinase assay, resulted in the isolation of five phenylethanoid glucosides and four iridoid glycosides. Two of them, 2′‐O‐acetylisoplantamajoside and 2′,6″‐O‐diacetylisoplantamajoside, represent new natural products. Evaluation of the inhibitory activity of all isolated compounds revealed that the observed activity is not related to the isolated phenylethanoid glycosides but mainly due to the presence of the iridoid glycoside globularin (IC₅₀ 41.94 μm ; CI_95% ± 16.61/11.89 μm ). Interestingly, structurally close related compounds (globularicisin, baldaccioside, and isoscrophularioside) showed no or only a weak tyrosinase inhibitory activity.     

Chemical constituents of Barleria prionitis and their enzyme inhibitory and free radical scavenging activities

From the aerial parts of Barleria prionitis, one new phenylethanoid glycoside, barlerinoside (1) along with six known iridoid glycosides, shanzhiside methyl ester (2), 6-O-trans-p-coumaroyl-8-O-acetylshanzhiside methyl ester (3), barlerin (4), acetylbarlerin (5), 7-methoxydiderroside (6), and lupulinoside (7) were isolated. Structures of these compounds were elucidated with the aid of extensive NMR spectral studies and chemical reactions. Compound 1 was significantly active in glutathione S-transferase (GST) inhibition assay with an IC₅₀ value of 12.4 μM but weakly active in acetylcholinesterase (AChE) inhibition assay. Compounds 2–7 also exhibited different levels of GST, AChE inhibitory and free radical scavenging activities.     

Impacts of glyphosate on photosynthetic behaviors in Kappaphycus alvarezii and Neosiphonia savatieri detected by JIP-test

Neosiphonia savatieri, a filamentous red alga, had spread and caused a massive death of its host Kappaphycus alvarezii since March 2009 in China. With an aim to found a specific method to eliminate the N. savatieri efficiently from carrageenan producing K. alvarezii, the effects of glyphosate on the photosynthetic behaviors of K. alvarezii and N. savatieri were comparatively studied by using fast chlorophyll a (Chl a) fluorescence kinetics. A dose- and time-dependent changes of fast Chl a fluorescence kinetics were obtained in N. savatieri treated by glyphosate, meanwhile no significant change was detected in the K. alvarezii under the same treatment conditions. Moreover, the maximum PSII photochemical efficiency for dark-adapted tissues (F _V/F _m) of N. savatieri decreased significantly when the N. savatieri was treated with glyphosate. Above results were further supported by transitory offshore glyphosate soak experiment. The brownish-red N. savatieri turned to be olivine then drew off within 5?days after soaking in >1?g?L^?1 of glyphosate for more than 1?min, meanwhile, no visible harmful effects were detected on K. alvarezii. Based on above results, glyphosate is suggested to be an effective chemical to eliminate N. savatieri from K. alvarezii.     

Iridoid and phenylethanoid glycosides in the New Zealand sun hebes (Veronica; Plantaginaceae)

The sun hebes are a small clade of New Zealand Veronica formerly classified as Heliohebe. The water-soluble compounds of Veronica pentasepala, Veronica raoulii and Veronica hulkeana were studied and 30 compounds including 15 iridoid glucosides, 12 phenylethanoid glycosides, the acetophenone glucoside pungenin, the mannitol ester hebitol II and mannitol were isolated. Of these, five were previously unknown in the literature: dihydroverminoside and 3,3′,4,4′-tetrahydroxy-α-truxillic acid 6-O-catalpyl diester, named heliosepaloside, as well as three phenylethanoid glycoside esters heliosides D, E and F, all derivatives of aragoside. The esters of cinnamic acid derivatives with iridoid and phenylethanoid glycosides and an unusually high concentration of verminoside were found to be the most distinctive chemotaxonomic characters of the sun hebes. The chemical profiles of the species were compared and used to assess the phylogenetic relationships in the group.     

Diabetes impairs heart mitochondrial function without changes in resting cardiac performance

Diabetes is a chronic disease associated to a cardiac contractile dysfunction that is not attributable to underlying coronary artery disease or hypertension, and could be consequence of a progressive deterioration of mitochondrial function. We hypothesized that impaired mitochondrial function precedes Diabetic Cardiomyopathy. Thus, the aim of this work was to study the cardiac performance and heart mitochondrial function of diabetic rats, using an experimental model of type I Diabetes. Rats were sacrificed after 28 days of Streptozotocin injection (STZ, 60 mg kg⁻¹, ip.). Heart O₂ consumption was declined, mainly due to the impairment of mitochondrial O₂ uptake. The mitochondrial dysfunction observed in diabetic animals included the reduction of state 3 respiration (22%), the decline of ADP/O ratio (∼15%) and the decrease of the respiratory complexes activities (22–26%). An enhancement in mitochondrial H₂O₂ (127%) and NO (23%) production rates and in tyrosine nitration (58%) were observed in heart of diabetic rats, with a decrease in Mn-SOD activity (∼50%). Moreover, a decrease in contractile response (38%), inotropic (37%) and lusitropic (58%) reserves were observed in diabetic rats only after a β‐adrenergic stimulus. Therefore, in conditions of sustained hyperglycemia, heart mitochondrial O₂ consumption and oxidative phosphorylation efficiency are decreased, and H₂O₂ and NO productions are increased, leading to a cardiac compromise against a work overload. This mitochondrial impairment was detected in the absence of heart hypertrophy and of resting cardiac performance changes, suggesting that mitochondrial dysfunction could precede the onset of diabetic cardiac failure, being H₂O₂, NO and ATP the molecules probably involved in mitochondrion-cytosol signalling.     

Vitamin D Deficiency Reduces Vascular Reactivity of Coronary Arterioles in Male Rats

Background: Vitamin D deficiency (VDD) may be considered an independent cardiovascular (CV) risk factor, and it is well known that CV risk is higher in males. Our goal was to investigate the pharmacological reactivity and receptor expression of intramural coronary artery segments of male rats in cases of different vitamin D supply. Methods: Four-week-old male Wistar rats were divided into a control group (n = 11) with optimal vitamin D supply (300 IU/kgbw/day) and a VDD group (n = 11, <0.5 IU/kgbw/day). After 8 weeks of treatment, intramural coronary artery segments were microprepared, their pharmacological reactivity was examined by in vitro microangiometry, and their receptor expression was investigated by immunohistochemistry. Results: Thromboxane A₂ (TXA₂)-agonist induced reduced vasoconstriction, testosterone (T) and 17-β-estradiol (E2) relaxations were significantly decreased, a significant decrease in thromboxane receptor (TP) expression was shown, and the reduction in estrogen receptor-α (ERα) expression was on the border of significance in the VDD group. Conclusions: VD-deficient male coronary arteries showed deteriorated pharmacological reactivity to TXA₂ and sexual steroids (E2, T). Insufficient vasoconstrictor capacity was accompanied by decreased TP receptor expression, and vasodilator impairments were mainly functional. The decrease in vasoconstrictor and vasodilator responses results in narrowed adaptational range of coronaries, causing inadequate coronary perfusion that might contribute to the increased CV risk in VDD.     

Blepharisides A and B,new flavonol glycosides from Blepharis ciliaris growing in Saudi Arabia

Bio-guided fractionation of the total MeOH extract (TME) of the aerial parts of Blepharis ciliaris (L.) B.L. Burtt. (Acanthaceae) growing in Saudi Arabia was carried out to evaluate its hepatoprotective activity against CCl₄-induced hepatotoxicity in rats. Successive chromatographic separations of the potent hepatoprotective n-BuOH fraction afforded two new flavonol glycosides, blepharisides A (1) and B (2), along with quercetin 3-O-rutinoside (3). Their structures were established by UV, IR, 1D, 2D NMR, and HRESIMS spectral data, in addition to comparison with literature data. Co-treatment of CCl₄ hepatic injured rats with the total MeOH extract (TME) and its fractions significantly restored the hepatic marker enzymes and total bilirubin to near-normal values compared to silymarin (reference drug). The isolated compounds were evaluated for their antioxidant and anti-inflammatory activities. They displayed significant antioxidant activity (DPPH assay) in relation to propyl gallate (positive control) (% inhibition of 88.2, 87.9, and 74.2, respectively). Compounds 1 and 2 demonstrated anti-inflammatory effects in the carrageenin induced paw edema method at a dose of 10 mg/kg.     

Unusual new phenylethanoid and phenylpropanoid diglycosides from the leaves of Chloranthus spicatus (Thunb.) Makino

Chloranthus spicatus (Thunb.) Makino (Chloranthaceae) has been used to treat aches, trauma, and bleeding in Traditional Chinese Medicine. Phytochemical investigation of the leaves of this plant led to the isolation an unusual new phenylethanoid diglycoside, spicaoside (1), and a new phenylpropanoid diglycoside, 1-allyl-3-methoxy-4- [apiofuranosyl(1 ⿿ 2)-glucopyranosyloxybenzene] (2), along with two known sesquiterpenoid glycosides, chloranoside A (3) and chloranthalactone E 8-O-β-d-glucopyranoside (4). Their structures were established by spectroscopic means. New compounds 1 and 2 showed moderate tyrosinase inhibitory activities with the IC₅₀ value of 15.4 μM and 29.1 μM. This study represents the first report of glycoside from C. spicatus.     

Protective effects of purified safflower extract on myocardial ischemia in vivo and in vitro

Carthamus tinctorius L. (safflower) is one of the most commonly used Chinese herbal medicines to prevent and treat cardiac disease in clinical practice. However, the mechanisms responsible for such protective effects remain largely unknown. In this study, we investigated the anti-myocardial ischemia effects of a purified extract of C. tinctorius (ECT) both in vivo and in vitro. An animal model of myocardial ischemia injury was induced by left anterior descending coronary artery occlusion in adult rats. Pretreatment with ECT (100, 200, 400, 600 mg/kg body wt.) could protect the heart from ischemia injury by limiting infarct size and improving cardiac function. In the in vitro experiment, neonatal rat ventricular myocytes were incubated to test the direct cytoprotective effect of ECT against H₂O₂ exposure. Pretreatment with 100–400 μg/ml ECT prior to H₂O₂ exposure significantly increased cell viability as revealed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. ECT also markedly attenuated H₂O₂-induced cardiomyocyte apoptosis, as detected by Annexin V and PI double labeling with flow cytometry. The intracellular level of reactive oxygen species (ROS) was shown by 2′,7′-dichlorofluorescin diacetate (DCFH-DA), and ECT pretreatment significantly inhibited H₂O₂-induced ROS increase. We made a preliminary examination of the signaling cascade involved in ECT mediated anti-apoptotic effects. Phosphatidylinositol 3 kinase (PI3K) inhibitor (LY294002) blocked the cytoprotective effect conferred by ECT. Taken together, our findings provide the first evidence that the cardioprotective effects of ECT in myocardial ischemia operate partially through reducing oxidative stress induced damage and apoptosis. The protection is achieved by scavenging of ROS and mediating the PI3K signaling pathway.     

Neuroprotective and Antioxidative Effect of Cactus Polysaccharides In Vivo and In Vitro

Cactus polysaccharides (CP), some of the active components in Opuntia dillenii Haw have been reported to display neuroprotective effects in rat brain slices. In the present study, we investigated the neuroprotective properties of CP and their potential mechanisms on brain ischemia-reperfusion injury in rats, and on oxidative stress-induced damage in PC12 cells. Male Sprague–Dawley rats with ischemia following middle cerebral artery occlusion and reperfusion were investigated. CP (200 mg/kg) significantly decreased the neurological deficit score, reduced infarct volume, decreased neuronal loss in cerebral cortex, and remarkably reduced the protein synthesis of inducible nitric oxide synthase which were induced by ischemia and reperfusion. Otherwise, the protective effect of CP was confirmed in in vitro study. CP protected PC12 cells against hydrogen peroxide (H₂O₂) insult. Pretreatment with CP prior to H₂O₂ exposure significantly elevated cell viability, reduced H₂O₂-induced apoptosis, and decreased both intracellular and total accumulation of reactive oxygen species (ROS) production. Furthermore, CP also reversed the upregulation of Bax/Bcl-2 mRNA ratio, the downstream cascade following ROS. These results suggest that CP may be a candidate compound for the treatment of ischemia and oxidative stress-induced neurodegenerative disease.     

Buthionine sulfoximine causes endothelium dependent hyper-relaxation and hypoadiponectinemia

A close relationship between oxidative stress, endothelial dysfunction, and hypoadiponectinemia has been observed. The present study was performed to investigate how glutathione depletion via buthionine sulfoximine (BSO) administration affects endothelial function and adiponectin levels in rats. Acetylcholine (Ach)-induced vasodilation was significantly enhanced in BSO-treated rats, compared with control rats. This was completely abolished by L-NAME, and Ach-induced vasodilation was not observed in the aorta without endothelium. These results suggest that Ach-induced hyper-relaxation of the aorta in BSO-treated rats is completely dependent on the presence of endothelium and mediated by changes in eNOS activity. Catalase significantly inhibited this relaxation to Ach and no effect of catalase on sodium nitroprusside-induced relaxation of the aorta without endothelium was observed in BSO-treated rats. Thus, hyper-relaxation of the aorta in BSO-treated rats is likely caused by H₂O₂ in addition to NO produced by the endothelium via an eNOS-dependent mechanism. Hypoadiponectinemia and decreased levels of adiponectin mRNA in adipose tissue were observed in BSO-treated rats. Protein expression of eNOS and SODs (SOD-1 and SOD-2) in the aorta was increased and plasma NOx levels were decreased in BSO-treated rats. Our results suggest that oxidative stress induced by BSO causes eNOS uncoupling and hyper-relaxation by producing H₂O₂, and that BSO-induced oxidative stress causes hypoadiponectinemia, probably by increasing H₂O₂ production in adipose tissue.     

Increased resistance to hydrogen peroxide‐induced cardiac contracture is associated with decreased myocardial oxidative stress in hypothyroid rats

The purpose of this study was to determine whether decreased oxidative stress would increase the resistance to cardiac contracture induced by H₂O₂ in hypothyroid rats. Male Wistar rats were divided into two groups: control and hypothyroid. Hypothyroidism was induced via thyroidectomy. Four weeks post surgery, blood samples were collected to perform thyroid hormone assessments, and excised hearts were perfused at a constant flow with or without H₂O₂ (1 mmol/L), being divided into two sub‐groups: control, hypothyroid, control + H₂O₂, hypothyroid + H₂O₂. Lipid peroxidation (LPO) was evaluated by chemiluminescence (CL) and thiobarbituric acid reactive substances (TBARS) methods, and protein oxidation by carbonyls assay in heart homogenates. Cardiac tissue was also screened for superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) activities, and for total radical‐trapping antioxidant potential (TRAP). Analyses of SOD and glutathione‐S‐transferase (GST) protein expression were also performed in heart homogenates. Hypothyroid hearts were found to be more resistant to H₂O₂‐induced contracture (60% elevation in LVEDP) as compared to control. CL, TBARS, carbonyl, as well as SOD, CAT, GPx activities and TRAP levels were reduced (35, 30, 40, 30, 16, 25, and 33%, respectively) in the cardiac homogenates of the hypothyroid group as compared to controls. A decrease in SOD and GST protein levels by 20 and 16%, respectively, was also observed in the hypothyroid group. These results suggest that a hypometabolic state caused by thyroid hormone deficiency can lead to an improved response to H₂O₂ challenge and is associated with decreased oxidative myocardial damage. Copyright © 2009 John Wiley & Sons, Ltd.     

Exogenous hydrogen peroxide enhanced the thermotolerance of Festuca arundinacea and Lolium perenne by increasing the antioxidative capacity

Heat stress is one of the most detrimental environment stresses for plants. Hydrogen peroxide (H₂O₂) is produced quickly in response to various stresses and likely plays a positive role in transmitting stress signal in organisms. This investigation addressed whether an exogenous H₂O₂ application would affect the heat response of turfgrasses and induce acclimation. Tall fescue (Festuca arundinacea cv. Barlexas) and perennial ryegrass (Lolium perenne cv. Accent), two important cool-season turfgrasses and forages, were sprayed with 10 mM H₂O₂ before they were treated with heat stress (38/30 °C, day/night) and compared with plants maintained at control temperatures (26/15 °C, day/night). Prior to the initiation of heat stress, H₂O₂ pretreatment increased the activities of guaiacol peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR) and glutathione-dependent peroxidase (GPX) and the ascorbate and glutathione pool, and it decreased the GSH/GSSG ratio. During the heat stress process, pretreated plants from both grasses exhibited higher turfgrass quality and relative water content, and they experienced lower oxidative damage and H₂O₂ levels. Moreover, the activities of APX, GR, GPX and glutathione-S-transferase increased significantly in response to H₂O₂ pretreatment under heat stress. These results suggested that H₂O₂ most likely participated in the transduction of redox signaling and induced the antioxidative defense system, including various enzymatic and nonenzymatic H₂O₂ scavengers. The scavengers played important roles in improving the thermotolerance of tall fescue and perennial ryegrasses.     

Middle-aged rats orally supplemented with gel-encapsulated catechin favorably increases blood cytosolic NADPH levels

Green tea catechins are primarily known to function as free radical scavengers and have several beneficial uses. Orally supplemented catechin (OSC) was previously shown to increase mitochondrial heme and catalase levels in rat heart blood, however, its effect in the cytosol has not been elucidated. Here, we determined the effects of OSC in the rat heart blood cytosol. We used middle-aged (40 week-old) and young (4 week-old) rats throughout the study. We isolated blood cytosol, verified its purity, and determined heme, hydrogen peroxide (H₂O₂) levels, catalase (CAT) activities, gp91^phox amounts, NADP and NAD pools, sirtuin 1 (SIRT1) and glutathione reductase (GR) activities, and free fatty acids (FFA). We established that OSC is associated with decreased heme-dependent H₂O₂ amounts while increasing heme-independent CAT activity. Moreover, we found that OSC-related decrease in NAD⁺ amounts among middle-aged rats is associated to increased NADPH levels and SIRT1 activity. In contrast, we associated OSC-related decrease in NAD⁺ amounts among young rats to decreased NADPH levels and increased SIRT1 activity. This highlights a major difference between catechin-treated middle-aged and young rats. Furthermore, we observed that cytosolic FFA and GR levels were significantly increased only among OSC-treated middle-aged rats which we hypothesize are related to increased NADPH levels. This insinuates that OSC treatment allows higher catechin amounts to enter the bloodstream of middle-aged rats. We propose that this would favorably increase NADPH amounts and lead to the simultaneous decrease in NADPH-related pro-oxidant activity and increase in NADPH-related biomolecules and anti-oxidant activities.     

Role of Orai1 and L-type CaV1.2 channels in Endothelin-1 mediated coronary contraction under ischemia and reperfusion

Ischemia and Reperfusion (I/R) injuries are associated with coronary artery hypercontracture. They are mainly originated by an exacerbated response to agonists released by endothelium such as Endothelin (ET-1), involving the alteration in intracellular calcium handling. Recent evidences have highlighted the implication of Store-Operated Calcium Channels (SOCC) in intracellular calcium homeostasis in coronary artery. However, little is known about the role of SOCC in the regulation of coronary vascular tone under I/R.The aim of this study was to evaluate the role of SOCC and l-type Ca²⁺ channels (LTCC) in coronary artery vasoconstriction originated by ET-1 in I/R. We used Left Anterior Descendent coronary artery (LAD) rings, isolated from Wistar rats, to study the contractility and intracellular Ca²⁺ concentration ([Ca²⁺]_i) under a simulated I/R protocol. We observed that responses to high-KCL induced depolarization and caffeine-induced Ca²⁺ release are attenuated in coronary artery under I/R. Furthermore, ET-1 addition in ischemia promotes transient and small rise of [Ca²⁺]_i and coronary vascular tone. Meanwhile, these effects are significantly potentiated during reperfusion. The resulting ET-1-induced vasoconstrictions and [Ca²⁺]_i increase were abolished by; GSK-7975A and gadolinium, inhibitors of SOCC; and nifedipine a widely used inhibitor of LTCC. Interestingly, using in situ Proximity Ligation Assay (PLA) in isolated coronary smooth muscle cells we found significant colocalization of LTCC Ca_V1.2 isoform with Orai1, the pore forming subunit of SOCC, and TRPC1 under I/R.Our data suggest that hypercontraction of coronary artery induced by ET-1 after I/R involves the co-activation of LTCC and SOCC, which colocalize significantly in the sarcolemma of coronary smooth muscle cells.     

The role of H2O2 formation in the insulin-like and insulin antagonistic effects on fat cells of omega-aminoalkyl glycosides.

A class of ω-aminoalkyl glycosides previously found to antagonize insulin's action on glucose oxidation in fat cells and to stimulate glucose oxidation in insulin's absence is now shown to mimic insulin also on the conversion of glucose to free fatty acids and to glycerol and glycerides. These glycosides also act like insulin by inhibiting hormone- and cholera toxin-stimulated lipolysis. Various lines of evidence demonstrate that most, if not all, of the insulin-like activity of these glycosides results from H₂O₂ formed from an amine oxidase-catalyzed oxidation of the aminoalkyl moiety of these compounds. A contaminant in the bovine plasma albumin (BPA) preparations used in the bioassays was found to represent a major source of the amine oxidase activity. Membrane (ghost) preparations were also found to possess amine oxidase activity capable of forming H₂O₂ from the glycosides in amounts sufficient to express insulin-like activity. Preliminary experiments with intact adipocytes suggest that this activity is located on the cell surface. The BPA-associated activity corresponds to the known Cu²⁺-containing “plasma-type” amine oxidase (EC 1.4.3.6) on the basis of its substrate specificity and susceptibility to selective inhibitors. The plasma membrane activity appears to correspond to neither the plasma-type nor to the flavin-containing mitochondrial-type (EC 1.4.3.4) and remains to be identified. The observed potent antilipolytic effects of both H₂O₂ and the aminoalkyl glycosides points out that any mechanism used to explain the insulin-like action of H₂O₂ must account for this ability to inhibit lipolysis as well as to stimulate glucose utilization. That catalase inhibits the insulin-like action of the glycosides and H₂O₂, but not that of insulin indicates that insulin's action is not mediated by cell surface-produced H₂O₂. Also, since the insulin antagonistic activity of these glycosides was not inhibited by catalase, H₂O₂ formation is not responsible for this antagonism. The latter finding, added to present and previous evidence on the carbohydrate structural requirements involved in H₂O₂ production and in the insulin-like biological and binding properties of the aminoalkyl glycosides, is consistent with a role(s) for their carbohydrate moieties in both the insulin antagonistic and agonistic activities of these compounds.