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Summary— The regulation and role of the intracellular Ca2+ pools were studied in rat peritoneal mast cells. Cytosolic free calcium concentration ([Ca2+ ]i) was monitored in fura-2 loaded mast cells. In the presence of Ca2+ and K+, compound 48/80 induced a biphasic increase in [Ca2+ ]i composed of a fast transient phase and an apparent sustained phase. The sustained phase was partially inhibited by the addition of Mn2+ . DTPA, a cell-impermeant chelator of Mn2+ , reversed this inhibition, suggesting that a quenching of fura-2 fluorescence occurs in the extracellular medium. In the absence of extracellular Ca2+ , the transient phase, but not the sustained one, could be preserved, provided that mast cells were depolarized. The transient phase was completely abolished by thapsigargin, a microsomal Ca2+ -ATPase inhibitor. Maximum histamine release induced by either compound 48/80 or antigen was obtained in the absence of added Ca2+ only when mast cells were depolarized. These histamine releases were inhibited by low doses (< 30 nM) of thapsigargin. Thapsigargin at higher doses induced histamine release which was unaffected by changing the plasma membrane potential, but was completely dependent on extracellular Ca2+ , showing that a Ca2+ influx is required for thapsigargin-induced exocytosis. Together, these results suggest that the mobilization of Ca2+ from thapsigargin sensitive-intracellular pools induced by compound 48/80 or antigen is sufficient to trigger histamine release. The modulation of these pools by the plasma membrane potential suggest their localization is close to the plasma membrane. 相似文献
5.
The antimutator phenotype, reportedly conferred by disruption of the Saccharomyces cerevisiae DDR48 gene, was suggested to affect only a specific spontaneous mutational pathway. We attempted to identify the types of mutation that are DDR48-dependent by determining the specificity of the ddr48 antimutator. However, disruption of DDR48 did not decrease the rates of spontaneous forward mutation in a plasmid-borne copy of the yeast SUP4-o gene, the reversion or suppression of the lys2–1 allele, or forward mutation at the CAN1 locus. Interestingly, the latter gene had been reported previously to be subject to the antimutator effect. DNA sequence analysis of spontaneous SUP4-o mutations arising in DDR48 and ddr48 backgrounds provided no evidence for a reduction in the rates of individual mutational classes. Thus, we were unable to verify that disruption of DDR48 causes an antimutator phenotype. 相似文献
6.
本文研究了蛛网膜下腔注射神经降压素(neurotensin,NT)对大鼠血压和心率的影响,结果表明:注射NT后血压立即下降,继而有所回升,但不及正常水平,然后再次降低,持续60min;心率无明显改变。H1受体阻断剂苯海拉明能部分阻断NT的降血压效应,H2受体阻断剂甲氰咪胍无翻转作用。注射组胺释放剂Compound48/80使血压下降,待血压恢复正常水平后,再注射NT,其降压效应减弱。结果提示:蛛网 相似文献
8.
Anita Sydbom 《Naunyn-Schmiedeberg's archives of pharmacology》1988,338(5):567-572
Summary Rat peritoneal mast cells were exposed to the neurohormone and basic opioid peptide -endorphin. -Endorphin induced a dose-dependent release of histamine from the mast cells. A significant histamine release was found at 5 mol/l of -endorphin and maximal release (35% of total) at 20 mol/l. The histamine release process was very rapid and terminated within 30 s at 37°C, and in this sense is very similar to the histamine release induced by compound 48/80 or neurotensin. The histamine release was temperature-dependent showing an optimum release around 30°C, and it was independent of available extracellular calcium, but was inhibited in the presence of high extracellular calcium concentrations. Naloxone, only in very high concentrations (10 mmol/l), inhibited the release, and the very same concentration also inhibited the neurotensin — as well as the compound 48/80-induced histamine release. Cromoglycate and benzalkoniumchloride, a 48/80 antagonist, both produced a progressive dose-dependent inhibition of -endorphin-, neurotensin- as well as compound 48/80-induced histamine release. Taken together, the findings indicate that the opioid peptide -endorphin induces a selective, energy-dependent release of histamine from peritoneal rat mast cells. The pattern of release has much in common with that of compound 48/80 and other basic peptides, such as neurotensin and substance P. In addition this pattern of release is similar to that induced by dynorphin.
Send offprint requests to Anita Sydbom at the above address 相似文献
9.
The ability of thiols to reduce 3-azidothymidine (AZT) to 3-aminothymidine has been investigated. Incubation with glutathione, dithiothreitol (DTT), or mercaptoethanol at pH 7.2 and 37°C leads to quantitative reduction of the azido moiety to an amine. The reaction is first order in AZT and first order in reducing agent (mono- or dithiol). The second-order rate constants are 2.77 × 10–3, 6.55 × 10–5, and 6.35 × 10–6
M
–l sec–1 for the dithiothreitol, glutathione, and mercaptoethanol reductions, respectively. The thiol reduction of alkyl azide to amine under mild conditions is a synthetic method particularly suitable for water-soluble azido compounds that are sensitive to catalytic hydrogenation. The potential for the mono- or dithiol-mediated reduction of alkyl azides under biological conditions must be considered when conducting studies of azido drugs. 相似文献
10.
Domenico Ribatti Renato Contino Fabio Quondamatteo Vittoria Formica Alfredo Tursi 《Anatomy and embryology》1992,186(3):241-244
Summary Two mast cell populations, connective tissue mast cells (CTMCs) and mucosal mast cells, (MMCs) containing different proteoglycans in their granules, can be distinguished in several animal species by means of histochemical methods. In this study we documented the presence of these two types of mast cell in the chick embryo lung, from the 15th incubation day for the MMCs, and from the 18th incubation day for the CTMCs. Lungs of embryos treated with compound 48/ 80, which produces degranulation of the CTMCs, showed a decrease in the number of this type of mast cell and an unchanged number of MMCs. In the lungs of embryos treated with dexamethasone, which degranulates MMCs, a reduction in the number of these cells and an unchanged number of the CTMs were found. 相似文献