共查询到20条相似文献,搜索用时 31 毫秒
1.
G.B. Graybar J.K. Harrington K.H. Cowen E.W. Spannhake A.L. Hyman D.B. McNamara P.J. Kadowitz 《Prostaglandins & other lipid mediators》1986,31(1)
The effects of leukotriene D4 (LTD4) on pulmonary mechanics were investigated in anesthetized, paralyzed cats under conditions of controlled ventilation. Intravenous injections of LTD4 in doses of 3, 10, and 30 μg caused significant increases in transpulmonary pressure (PTP) and lung resistance (RL) while decreasing dynamic compliance (Cdyn). LTD4 also increased systemic arterial pressure (PA0). The changes in PTP, RL, and Cdyn in response to LTD4 were blocked by sodium meclofenamate, a cyclooxygenase inhibitor. However, there was no significant change in the increase in PA0 following cyclooxygenase blockade. U 46619, a thromboxane mimic, was 30 to 100 times more potent than LTD4 in increasing PTP, RL and decreasing Cdyn in the cat. These data show that LTD4 has significant smooth muscle constrictor activity in central airways as well as peripheral portions of the feline lung. In addition, these data suggest that in the cat the actions of intravenously administered LTD4 on lung mechanics are mediated by release of cyclooxygenase products while the systemic pressor effects are not dependent upon the integrity of the cyclooxygenase pathway. 相似文献
2.
The contractile activities of peptide leukotrienes (LT) on isolated spiral strips of ferret trachea were chracterized pharmacologically. LTC4 and LTD4 contracted ferret tracheal strips in a concentration-related manner and were 3- to 8-fold more potent than carbachol. In contrast, high concentrations of LTE4 evoked either weak contraction or none at all, whereas LTC4 and D4 were partial agonists compared to carbachol. In tissues which were unresponsive to LTE4, this compound antagonized contractile responses to LTC4 and D4 in an apparently competitive manner: Carbachol-induced contractions were not altered by LTE4. The cyclooxygenase inhibitor, indomethacin (5 μM), LT antagonists, FPL55712 (10 μM), atropine (1 μM), phenoxybenzamine (10 μM), and LTB4 (10 μM) failed to alter LTC4 and D4 concentration-response curves. The results in dicate that ferret trachea is sensitive to the contractile activity of LTC4 and LTD4 but not LTE4. The LT-induced contractions appear to be mediated by a direct action of the LT rather than indirectly through release of secondary mediators such as thromboxane, prostaglandin, or acetylcholine. LT receptors in ferret trachea are insensitive to FPL55712 but are antagonized by LTE4. 相似文献
3.
William E. Hageman Michael P. Rose Francis J. Persico 《Prostaglandins & other lipid mediators》1986,32(4):563-577
5,8,11,14-Eicosatetraynoic acid (ETYA), a compound which inhibits both the cyclooxygenase and lipoxygenase pathways of arachidonic acid metabolism, antagonized the contraction of segments of guinea-pig ileal longitudinal muscle produced by SRS-A (IC50 = 2.73 μM). This activity was unaffected by pretreatment of the tissues with 10 μM indomethacin. Phenidone, another mixed cyclooxgenese-lipoxygenese inhibitor, was inactive. FPL-55712, an SRS-A antagonist, was a very potent inhibitor (IC50 = 0.011 μM).BW755C and NDGA nonselectively inhibited the contractions of the guinea-pig ileal longitudinal muscle induced by SRS-A or histamine.ETYA antagonized the contraction of the guinea-pig ileal strip produced by 6 nM synthetic LTC4 (IC50 = 9.3 μM). FPL-55712 demonstrated an IC50 of 0.3 μM in a similar series of experiments. ETYA, 1, 3 or 10 μM did not inhibit the contractions elicited by 0.5 μM of histamine.This was not a tissue-selective effect since 100 μM ETYA antagonized the LTC4-induced contraction of the guinea-pig lung parenchymal strip preparation.These data demonstrate that ETYA antagonized the contractile effect of the leukotrienes on tissues from the gastrointestinal tract and lung. Furthermore, the inability of indomethacin or phenidone to inhibit the contractile response suggests that antagonism by ETYA may occur by a mechanism independent of cyclooxygenase and lipoxygenase enzymes. 相似文献
4.
《Prostaglandins, Leukotrienes and Medicine》1982,8(2):157-170
The mechanism of action of LTB4 has been investigated on the guinea-pig lung parenchymal strip. Mepacrine (20 ug/ml), an inhibitor of phospholipase A2, abolished the action of LTB4 on parenchymal strips. Eicosatetraynoic acid (10 ug/ml) and BW755C (40 ug/ml) which are inhibitors of cyclooxygenase and lipoxygenase pathways, produced a marked inhibition of the lung strip contraction to LTB4. Similarly, aspirin (30 ug/ml) and flufenamate (lug/ml) showed a strong inhibition of the contraction of parenchymal strips to LTB4; these results suggested that cyclooxygenase products mediate the action of LTB4. The response to LTB4 was unaffected by 15-hydroperoxyeicosatatraenoic acid (15-HPETE; 1 ug/ml) while L8027 (25 ng/ml) reduced the contraction by 50%, suggesting that thromboxane A2 rather than prostacyclin was involved. Since parenchymal strips do not appear to be very sensitive to PGF2α, PGE2 and the endoperoxides, and since effluents from LTB4-treated lungs produced contractions of lung strip and rabbit aorta which were reduced after 5 min. at 250, thromboxane A2 was postulated to mediate the lung effect of LTB4. The release of thromboxane B2 (TxB2) from lungs stimulated with LTB4 was confirmed by gaschromatography-mass spectrometric (GC-MS) analyses. 相似文献
5.
R. Hamel P. Masson A.W. Ford-Hutchinson T.R. Jones G. Brunet H. Piechuta 《Prostaglandins & other lipid mediators》1982,24(3)
Leukotriene D4 (LTD4) when administered intravenously or by aerosol to guinea pigs produced changes in pulmonary mechanics including a decrease in dynamic compliance and an increase in pulmonary resistance. The effects of intravenous LTD4 (0.5 μg kg−1) were short lived and abolished by pretreatment of the animal with either cyclooxygenase inhibitors, a thromboxane synthetase inhibitor (OKY 1555) or an SRS-A antagonist (FPL 55712). These findings suggest that bronchoconstriction produced by the intravenous infusion of LTD4 at 0.5 μg kg−1 is due to the release of thromboxane A2. However, in animals treated with indomethacin, LTD4 at higher doses (>0.8 μg kg−1) still elicited a bronchoconstriction which could be blocked by FPL 557112. Nebulization of 0.1 – 1.0 μg of LTD4 into the lung produced prolonged changes in pulmonary mechanics which were inhibited by FPL 55712 and were potentiated indomethacin. LTD4, therefore, when administered by aerosol produced effects on the lung which were not mediated by cyclooxygenase products. Responses to nebulized rather than intravenous LTD4 in the guinea pig may more closely resemble those seen in human tissues. 相似文献
6.
Mary E. Gerritsen David O. Morgan Thomas P. Parks Morton P. Printz Karl P. Lederis 《Prostaglandins & other lipid mediators》1981,22(6):873-892
Urotensin I (UI) elicits dose-dependent relaxation responses in isolated helical strips of rat tail and mesenteric arteries contracted by 10−5M norepinephrine (NE). The rat mesenteric artery demonstrated a 40 fold lower threshold sensitivity to UI (0.25 mU/M1 versus maximal relaxation at 0.25 mU/m1). Complete relaxation of the rat tail artery with UI could not be achieved, even at doses exceeding 10 mU/m1. Pretreatment of the arterial strips with cyclooxygenase inhibitors had no effect on the contractile response to NE in the tail artery, but reduced NE responsiveness in the mesenteric artery. Significant enhancement of UI relaxation responses in both types of arterial strips was achieved by pre-treatment with the cyclooxygenase inhibiters, suggesting a modulatory role for prostaglandins (PGs) in the expression of the UI relaxation response in NE contracted arterial strips. The major enzymatically formed PG (as assessed by [1-14C] PGH2 metabolism in broken cell preparations) in both the rat tail and mesenteric arteries was 6-keto PGF1α, the stable hydrolysis product of PGI2. Using a specific RIA to quantify 6-keto PGF1α release, it was found that UI elicited nearly a two-fold increase in the release of this PG compared to the NE control in both rat tail and mesenteric arteries. These data suggest that PGI2 may modulate the relaxation response to UI either by direct physiological opposition (PGI2 elicited contractile response in NE contracted tail and mesenteric arteries at doses exceeding 10−8M) and/or by some as yet undefined mechanism (eg. effects on Ca2+, cAMP). 相似文献
7.
Dennis B. McNamara Julie K. Harrington John A. Bellan Gwendolyn B. Graybar David C. Underwood Philip J. Kadowitz 《Molecular and cellular biochemistry》1989,85(1):29-41
The effects of CGS 13080, a thromboxane (TXA2) synthase inhibitor, on airway responses to arachidonic acid (AA) were investigated in the anesthetized cat. Feline and human lung microsomal fraction exhibited prostaglandin I2 (PGI2, prostacyclin), and TXA2 synthase activities, and human platelet microsomal fractions exhibited TXA2 synthase activity. Cat and human lung microsomal fractions, but not human platelets, exhibited the presence of GSH-dependent PGE2 isomerase activity. CGS 13080 inhibited TXA2 synthase activity in all three microsomal fractions in a concentration-dependent manner. The increases in transpulmonary pressure and lung resistance and decreases in dynamic compliance in response to AA were decreased significantly by CGS 13080. These data suggest that the bronchoconstrictor actions of AA are mediated in large part by the formation of TXA2. The data further indicate that cyclooxygenase products other than TXA2 are involved in the bronchoconstrictor response to AA since meclofenamate had greater inhibitory activity than did CGS 13080. Moreover, the effects of CGS 13080 were due to inhibition of TXA2 synthase rather than an effect on TXA2 receptors, since airway responses to the TXA2 mimic, U46619, were not altered. The present data show that CGS 13080 inhibits TXA2 synthase activity without altering cyclooxygenase, PGI2 synthase, or GSH-dependent PGE2 isomerase activities. The data further indicate that in vivo administration of CGS 13080 may selectively increase PGI2 synthase activity. 相似文献
8.
In various gastrointestinal smooth muscles, two different muscarinic receptor subtypes, M2 and M3, are expressed; these receptors are the target for the parasympathetic neurotransmitter acetylcholine. Although the number of M2 receptors is much greater than that of M3 receptors, the functional role of the former receptor subtype has yet to be fully defined, since pharmacological analyses of the contractile responses to acetylcholine and other muscarinic agonists have revealed that such responses are mediated extensively by the minor M3 subtype. The M3 receptor links to Ca2+ store release, and the released Ca2+ ions may contribute to the contraction. However, many studies indicated the importance of Ca2+ influx through voltage-gated Ca2+ channels, rather than Ca2+ release, in muscarinic contractions, since the contractile responses are markedly inhibited by Ca2+ channel blockers. The major M2 receptors link to the opening of cationic channels leading to the membrane depolarization, which in turn activates voltage-gated Ca2+ channels. Thus, there should be somewhere a point of contact between the M3- and M2-mediated signal transductions, as if M3 receptor stimulation is connected with membrane depolarization. Our electrophysiological and pharmacological findings suggest that the M2-mediated cationic channel opening and a resulting increase in the membrane electrical activity are the primary mechanism for mediating the contractile response to muscarinic agonists. An allosteric interaction between M2 and M3 receptors such that M3 activation intensifies the M2/cation channel pathway may account at least in part for the failure of many previous analyses to detect M2 participation in the contractile responses to full agonists. 相似文献
9.
《Prostaglandins & other lipid mediators》1985,29(4):651-660
Radioimmunoassay and bioassay techniques have been used to investigate the ability of leukortriene (LT)F4 to release products of arachidonic acid metabolism from guinea pig isolated lungs perfused via the pulmonary artery. Also, the abilities of LTC4, LTD4 LTE4 and LTE4 to contract guinea pig ileal smooth muscle (GPISM) was studied. Each of the LT's contracted GPISM. The rank order of potency was LTD4 > LTC4 > LTE4 > > LTF4 in a ratio 1:7:170:280 respectively. Bioassay of pulmonary effluents indicated the passage of LTF4 through the lungs caused a contraction of rabbit aorta as well as an FPL-55712 sensitive contraction of GPISM. The contractions of rabbit aorta were inhibited by pretreatment of the lungs with Indomethacin but not with the thromboxane synthetase inhibitor Dazoxiben. Radioimmunoassay of the lung effluents indicated LTF4 to cause a 70-fold increase in thromboxane B2 (TXB2), 4-fold increase in prostaglandin (PG)E2 and a 16-fold increase in 6-keto PGF1α levels. The LTF4-induced increments of these immunoreactive metabolites was inhibited by pretreatment of the lungs with Indomethacin. Pretreatment of lungs with Dazoxiben inhibited the LTF4-induced increment in TXB2 and enhanced the effluet levels of PGE2 24-fold (compared with untreated lungs). There were no detectable differences in either immunoreactive LTC4 or immunoreactive LTB4 levels. It is concluded LTF4 is a relatively weak agonist on GPISM and can induce the release of cyclooxygenase products of arachidonic acid metabolism from guinea pig perfused lung. 相似文献
10.
The contractile activity of leukotriene B4 (LTB4), leukotriene D4 (LTD4) and histamine on strips of guinea pig lung parenchyma was shown to be dependent on the calcium concentrations of the Krebs solution. The calcium channel blocker verapamil (2.0 to 15uM) had an additive effect on the inhibitory activity of low calcium (0.1 mM) on contractions of guinea pig parenchyma to leukotrienes and histamine. Cobalt chloride, a divalent cation, also produced dose-dependent reductions of the myotropic activities of LTB4, LTD4 and histamine. An antagonist of calmodulin, triflouperazine (1–200 uM), dose-dependently inhibited the contractile activity of the three agonists on the parenchyma strip. The IC50 of this compound for inhibition of histamine was much lower (2–3uM) than the IC50 for inhibition of leukotrienes (75 uM). Valinomycin, a potassium ionophore, also interfere with the contractile activities of leukotrienes and histamine whereas a blocker of sodium channel, tetrodotoxin, had no effect on the activity of these agonists. Furthermore, an inhibitor of methyltransferase, 3-deazaadenosine, significantly diminished the responses of the parenchyma to leukotrienes and histamine. These results confirmed the important role of extracellular and intracellular calcium in the myotropic activity of leukotrienes and histamine in guinea pig lungs and showed that compunds which interfere either directly or indirectly with calcium mobilization into the lung smooth muscles, decreased the tissue responsiveness. 相似文献
11.
In order to examine the modulation of leukotriene (LT) release, the PAF-acether-mediated stimulation of these compounds in rat lung was studied. Release of LTC4, LTD4 and LTE4 in both perfused and chopped lung preparations was measured using HPLC and radioimmunoassay. Pre-incubation or pre-infusion of the tissue with indomethacin and PGE2 was conducted to investigate the effect of cyclooxygenase inhibitors and products on the lipoxygenase pathway. In addition, the effects of LT levels of pre-incubation with vasoactive intenstinal polypeptide (VIP) in chopped lung were observed.In perfused rat lung, indomethacin reduced the levels of LTC4 relative to LTD4 as measured in the first 2 min after stimulation of the lung by PAF-acether. Chopped lung preparations, incubated for 15 min. exhibited higher levels of LTC4 and LTD4 in indomethacin-treated samples, this increases being effectively reversed by PGE2.In the VIP pre-incubation experiments clear inhibition of peptido -leukotriene synthesis was observed, with no LTC4 and only low levels of LTD4 and LTE4 observed in VIP-incubated samples. In preliminary experiments using rabbit C5a des arg and PAF-acether on rabbit lung parenchyma strips to stimulaet LT release, disodium cromoglycate pre-incubation was observed to inhibit this release.Inhibition of the 5-lipoxygenase pathway of PGE2 is supported by these experiments. VIP appears to act as an inhibitor of LTC4 and LTD4 biosynthesis or release in this model. Too little is known that peptidergic actions to postulate a mechanism by which a neuroendocrine peptide exerts control of release of arachidonate metabolites; however, VIP is associated with muscarinic stimulation (1) and has been found in mast cells (2). 相似文献
12.
13.
In the presence of indomethacin, Leukotriene C4 (LTC4), LTD4 and LTE4 were shown to be contractile agents
on guinea pig gall bladder strips. The respective pD2 values for LTC4, LTD4 ad LTE4 were 9.1, 9.1 and 7.7. The contractile effects of LTD4 were not mediated through the generation of cyclooxygenase products and were antagonized by the SRS-A antagonist FPL-55712. The effects of PGE1, PGF2α, the endoperoxide analogue U44069 and histamine on gall bladder strips were also examined. All these agents caused dose-related contractions but were considerably less potent than the leukotrienes. Leukotrienes are therefore potent contractile agents on the guinea pig gall bladder and may contribute to gall bladder contractions or spasms
. 相似文献
14.
Effects of pure enantiomers of flurbiprofen in comparison to racemic flurbiprofen on eicosanoid release from various rat organs ex vivo. 总被引:2,自引:0,他引:2
The effects of oral treatment of rats with pure enantiomers of flurbiprofen in comparison to racemic flurbiprofen on ex vivo release of eicosanoids from gastric mucosa, jejunum, lung, brain and clotting whole blood were investigated. With the S(+) enantiomer and the racemate dose-dependent inhibition of release of cyclooxygenase products of arachidonate metabolism in all tissues tested was observed, while release of leukotriene (LT) C4 was inhibited in gastric mucosa, but not in jejunum and lung. On the other hand, the R(-) enantiomer inhibited cyclooxygenase in the various tissues less potently and to a variable degree with no significant effect in the jejunum. The R(-) enantiomer had no effect on LTC4 release from any of the tissues investigated. Furthermore, the effect of a high dose of 25 mg/kg of the S(+) enantiomer on release of cyclooxygenase products from the various tissues was much longer lasting than that of an identical dose of the R(-) enantiomer. Stereoselective pharmacokinetics of the flurbiprofen enantiomers and/or organ specific cyclooxygenase activities could underly these results. The more potent cyclooxygenase inhibition by the S(+) enantiomer correlates with its higher anti-inflammatory activity and gastrointestinal toxicity. On the other hand, both enantiomers have been shown previously to be almost equally effective analgesics. Inhibition of brain cyclooxygenase might contribute to this effect. 相似文献
15.
Induction of Prostanoid Biosynthesis by Bacterial Lipopolysaccharide and Isoproterenol in Rat Microglial Cultures 总被引:15,自引:11,他引:4
Abstract: We have used purified microglial cultures obtained from neonatal rat cerebral cortex to investigate the ability of microglia to release prostanoids after exposure to bacterial lipopolysaccharide, a classic macrophage activator. Release of prostaglandin E2, prostaglandin D2, and thromboxane A2 was low in basal conditions and increased in a dose- and time-dependent way upon lipopolysaccharide treatment (1–100 ng/ml), by a mechanism requiring de novo protein synthesis. When compared with astrocytes, microglial cells appeared to respond more effectively to lipopolysaccharide, being able to release prostanoids after exposure to a 100-fold lower concentration of lipopolysaccharide. In addition to prostanoids, we also measured the release of leukotriene B4; although lipopolysaccharide failed to stimulate leukotriene B4 release by microglial cells, it doubled the basal production in astrocytes. Lipopolysaccharide enhanced the release of preloaded [3H]arachidonic acid from microglial membrane phospholipids by a mechanism inhibited by the protein synthesis inhibitor cycloheximide, which suggests that the increased availability of arachidonic acid contributed to the enhanced prostanoid production. Lipopolysaccharide, however, also stimulated prostanoid synthesis by inducing cyclooxygenase activity, as shown by determining the activity of newly synthesized enzyme after inactivating the endogenous enzyme with aspirin and by assessing the level of the inducible form of cyclooxygenase by western blot analysis. Among the mechanisms potentially involved in the regulation of microglial prostanoid production, we studied the effect of β-adrenergic receptor activation. The β-agonist isoproterenol was inactive by itself but doubled the effect of lipopolysaccharide. The drug appeared to act mainly through the inducible cyclooxygenase; because it did not stimulate arachidonic acid release, it enhanced the lipopolysaccharide-evoked prostanoid production observed after aspirin pretreatment and induced de novo synthesis of cyclooxygenase detectable by western blot analysis. We suggest that during cerebral inflammatory processes microglia can contribute to the establishment of high prostanoid levels, which can be further elevated by β-adrenergic activation. 相似文献
16.
Arachidonic acid (AA) at 10?4M and 10?3M produced a phasic contraction in isolated canine basilar arteries that peaked rapidly and then slowly declined. This contraction was evidently due to the conversion of AA to prostanoids because it was blocked by cyclooxygenase inhibitors and because 11, 14, 17 eicosatrienoic acid (10?3M), which is not a cyclooxygenase substrate, failed to produce a contraction. When the artery was exposed to 10?3M AA for 20 min and washed, subsequent contractile responses to 10?6M serotonin (5-HT) were only 10% of control. Contractions produced by prostaglandin E2 (10?5M), uridine triphosphate (10?4M) and potassium (5.5×10?4M) were inhibited to a lesser degree than 5-HT, the response to potassium being the least affected (66% of control). This damaging effect of 10?3M AA did not occur if the artery was washed at peak contraction nor with 10?4M AA. Autooxidation products were evidently not responsible for the damage because prior oxygenation (90 min) of 10?4M AA had no such effect. Pretreatment with superoxide dismutase or ascorbate did not prevent the inhibition, suggesting that free radical reactions were not involved. Pretreatment with indomethacin (3×10?4M) or meclofenamate (10?4M) also failed to prevent the inhibitory phenomenon. Saponin, a detergent, produced similar inhibitory effects but 11, 14, 17 eicosatrienoic acid or oleate (10?3M) did not. The arteries partially recovered from the inhibition with time. In conclusion, AA produced contraction in basilar arteries by inducing prostaglandin synthesis but can produce secondarily by an unidentified mechanism an inhibition of the contractile responses evoked by various agonists that is both time and concentration dependent. 相似文献
17.
The purpose of this study was to learn wether a number of Ca2+ antagonists were effective in reducing contractile response of the isolated ileum of the sensitized and normal guinea pig. Contractions of the normal ileum in response to LTD4, acetylcholine, histamine, and potassium chloride were obtained before and after verapamil, diltiazen and papaverine. Ovalbumin-induced contractions of the ovalbumin-sensitized ileum were obtained in the presence of the three Ca2+ antagonists. In the normal ileum, all the Ca2+ antagonists were highly effective in diminishing the contractile responses to LTD4, acetylcholine, histamine and potassium chloride. In the sensitized ileum, ovalbumin-evoked contractions, with subsequent release of a potent contractile mediator (presumably SRS-A), were Ca2+-dependent since verapamil, diltiazem and papaverine caused a concentration-related reduction of contractions. Thus, the influx of extracellular Ca2+ plays a key role in the contractile responses of the normal and sensitized guinea pig ileum when stimulated by various potent agonists acting on specific receptors or on the cell membrane. 相似文献
18.
R.Robert Schellenberg Marilyn J. Duff Aidan Foster Harry B. Paddon 《Prostaglandins & other lipid mediators》1986,32(2)
Histamine caused a triphasic response of human pulmonary artery strips in vitro, consisting of a small initial contraction followed by pronounced relaxation preceding a second contractile response. These characteristics were not seen with other contractile stimuli including 5-hdyroxytryptamine, leukotriene D4, and KC1. The relaxant component of this response was ablated by removal of endothelium from the vascular strips or by pretreatment of the tissues with 1μM indomethacin. Measurement of the PGI2 degradation product 6-keto-PGF1α in supernatants from histamine-challenged tissues confirmed the synthesis of PGI2. Supernatants from unstimulated or leukotriene-challenged tissues contained no detectable amounts of 6-keto-PGF1α. The histamine H1 antagonist diphenhydramine inhibited both the contractile and relaxant responses to histamine whereas the H2 antagonist cimetidine affected neither component. The released PGI2 significantly altered the dose-respons curve to histamine without inhibiting the maximal contractile responses. We conclude that histamine induces PGI2 formation from pulmonary arterial endothelium via an H1 receptor. 相似文献
19.
I. V. Kubasov R. S. Arutyunyan E. V. Matrosova 《Journal of Evolutionary Biochemistry and Physiology》2016,52(1):46-55
Using a computer graphics approach, the last contractile responses (LCRN, where N is a number of elementary contractile responses in tetanus) were separated from integral tetanic responses of rat fast muscles, m. Eхtensor digitorum longus (m. EDL), and slow muscles, m. Soleus, evoked by trains of 5, 10 and 50 stimuli. In m. Soleus, at a stimulation frequency of 20 Hz, the LCR5 average amplitude decreased to 64 ± 9% compared to the single contraction amplitude. As N increased, LCRN recovered and then rose to the values exceeding almost twofold initial elementary contractile responses (up to 211 ± 10% for LCR50). Simultaneously, against the background of rising elementary contractile responses, a significant shortening of their half-decay time (~by 50%) and the formation of a stationary plateau within LCRN was observed. In m. EDL, at a stimulation frequency of 50 Hz, there was only a single-phase LCRN rise (up to 165 ± 18% for LCR50) without changes in half-decay time and plateau formation. In skeletal muscles of both types, the prolonged (up to 30 s) ‘hyper-relaxation effect’ was found to develop after the end of tetanic responses manifested as a reduction of muscle tension followed by its recovery to the initial level. Possible mechanisms of these events are discussed. It is hypothesized that transformation of elementary contractile responses in skeletal muscles can be fulfilled due to the existence of specialized microdomains in muscle fibers which regulate accumulation and extrusion of Ca2+ ions during tetanic activity. The possibility that the basic, depolarization-induced, Ca2+ release (DICR) is complemented by an additional, Ca2+-induced, Ca2+release (CIRC) is analyzed. 相似文献
20.
R. Hamel A.W. Ford-Hutchinson A. Lord M. Cirino 《Prostaglandins & other lipid mediators》1984,28(1):43-56
The chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine (F-met-leu-phe) was shown to be a potent myotropic agent on the guinea-pig parenchymal strip (IC50), 2 × 10−7 M). The response was unaffected by the histamine (H1) antagonist, mepyramine, but in the presence of the cyclooxygenease inhibitor, indomethacin, the dose response curve was shifted to the left (IC5, 4 × qo−8 M) and the maximal response reduced. Injection of F-met-leu-phe into perfused guinea pig lungs resulted in the release of leukotriene-like activity which was detected by superfusion over guinea-pig ileum preparations in the presence and absence of FPL-55712. Intravenous injection of F-met-leu-phe to spontaneously breathing anaesthetized guinea pigs resulted in transient increases in pulmonary resistance and blood pressure and decreases in dynamic compliance and heart rate. The pulmonary parameters were significantly inhibited by BW 755C, indomethacin, FPL-55712 and a contractile prostanoid antagonist, L-640,305. These results demonstrate that F-met-leu-phe is potent bronchoconstrictor in the guinea pig and that the peptide may induce these changes through the generation of products of the cyclooxygenase and lipoxygenase pathways of arachidonic acid metabolism. 相似文献