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61.
The ouabain-insensitive, Mg2+-dependent, Na+-stimulated ATPase activity present in fresh basolateral plasma membranes from guinea-pig kidney cortex cells (prepared at pH 7.2) can be increased by the addition of micromolar concentrations of Ca2+ to the assay medium. The Ca2+ involved in this effect seems to be associated with the membranes in two different ways: as a labile component, which can be quickly and easily ‘deactivated’ by reducing the free Ca2+ concentration of the assay medium to values lower than 1 μM; and as a stable component, which can be ‘deactivated’ by preincubating the membranes for periods of 3–4 h with 2 mM EDTA or EGTA. Both components are easily activated by micromolar concentrations of Ca2+. The of the system for Na+ is the same, 8 mM, whether only the stable component or both components, stable and labile, are working. In other words, the activating effect of Ca2+ on the Na+-stimulated ATPase is on the , and not on the of the system for Na+. The activating effect of Ca2+ may be related to some conformational change produced by the interaction of this ion with the membranes, since it can also be obtained by resuspending the membranes at pH 7.8 or by ageing the preparations. Changes in the Ca2+ concentration may modulate the ouabain-insensitive, Na+-stimulated ATPase activity. This modulation could regulate the magnitude of the extrusion of Na+ accompanied by Cl? and water that these cells show, and to which the Na+-ATPase has been associated as being responsible for the energy supply of this mode of Na+ extrusion. 相似文献
62.
The uptake of glycine in rabbit renal brush border membrane vesicles was shown to consist of glycine transport into an intravesicular space. An Na+ electrochemical gradient (extravesicular>intravesicular) stimulated the initial rate of glycine uptake and effected a transient accumulation of intravesicular glycine above the steady-state value. This stimulation could not be induced by the imposition of a K+, Li+ or choline+ gradient and was enhanced as extravesicular Na+ was increased from 10 mM to 100 mM. Dissipation of the Na+ gradient by the ionophore gramicidin D resulted in diminished Na+-stimulated glycine uptake. Na+-stimulated uptake of glycine was electrogenic. Substrate-velocity analysis of Na+-dependent glycine uptake over the range of amino acid concentrations from 25 μM to 10 mM demonstrated a single saturable transport system with apparent Km = 996 μM and Vmax = 348 pmol glycine/mg protein per min. Inhibition observed when the Na+-dependent uptake of 25 μM glycine was inhibited by 5 mM extravesicular test amino acid segregated dibasic amino acids, which did not inhibit glycine uptake, from all other amino acid groups. The amino acids d-alanine, d-glutamic acid, and d-proline inhibited similarly to their l counterparts. Accelerative exchange of extravesicular [3H]glycine was demonstrated when brush border vesicles were preloaded with glycine, but not when they were preloaded with l-alanine, l-glutamic acid, or with l-proline. It is concluded that a single transport system exists at the level of the rabbit renal brush border membrane that functions to reabsorb glycine independently from other groups of amino acids. 相似文献
63.
Using brush-border membrane vesicles isolated from calf kidney cortex the effect of tyrosine-reactive reagents on sodium-dependent d-glucose transport was investigated. Treatment of the membranes for 60 min with NBD-Cl (7-chloro-4-nitrobenzo-2-oxa-1,3-diazole), N-acetylimidazole or tetranitromethane decreased d-glucose uptake 50, 70 and 40%, respectively. Tracer exchange experiments revealed that the inhibition of transport is due to a direct modification of the sodium-d-glucose cotransport system. The modification by NBD-Cl decreases the apparent Vmax of the transport system with respect to its interaction with sodium. In addition, the rate of inactivation of the transport system by NBD-Cl is reduced in the presence of high concentrations of sodium. The results indicate that tyrosine residues play an essential role in sodium-d-glucose cotransport and are probably involved in the binding and/or transport of sodium by the sodium-d-glucose cotransport system. 相似文献
64.
Chemical carcinogens from several diverse chemical classes i.e.; aromatic amines, polycyclic hydrocarbons, nitrosamines, hormonal derivatives, metals and direct alkylating agents cause a 6.2–60.5-fold increase in the frequency of murine sarcoma virus (MSV)-induced transformation in a normal rat kidney (NRK) cell system. Exogenous metabolic activation with a rat liver S-9 homogenate is required for expression of this activity by procarcinogens. Non-carcinogenic analogs of these compounds fail to cause significant increases in the transformation frequency either with or without prior metabolic activation. Iododeoxyuridine, a mutagen also does not cause enhancement of transformation. This system may serve as the basis for a rapid and quantifiable means of identifying chemical carcinogens while introducing a new model for the understanding of the interactions between oncorna-viruses and chemical carcinogens. 相似文献
65.
Gary L. Bradshaw George R. Dubes 《In vitro cellular & developmental biology. Plant》1983,19(10):735-742
Summary Factors requred as supplements to basal tissue culture medium for the multiplication of cells of the cloned rat fibroblast
line called normal rat kidney 49F (NRK-49F) were identified as epidermal growth factor, fibronectin, insulin, and retinoic
acid. The requirement for fibronectin was manifested on a clean glass surface but not on the polystyrene plastic surface tested.
This set of required factors differs substantially from the factor sets required by the Madin-Darby, canine kidney (MDCK)
and LLC-PK1 pig kidney lines of epithelial cells and the baby hamster kidney 21 (BHK-21) line of fibroblasts. The serum-free medium supplemented
with the four factors supported rapid growth of NRK-49F cells when the initial cell population density was about 8,000 cells/cm2 or greater. At lower initial densities, cell multiplication was markedly increased by adding serum-free medium that had been
conditioned by NRK-49F cells. Cell growth rate in the defined serum-free medium stayed high through two serial passages but
declined in the third serial passage unless the cell-conditioned medium was added. 相似文献
66.
Neutral metalloendopeptidase associated with the smooth muscle cells of pregnant rat uterus 总被引:2,自引:0,他引:2
The pregnant rat uterus contains a membrane-bound metalloendopeptidase that is biochemically and immunologically similar to kidney enkephalinase (E.C.3.4.24.11). The uterus enzyme readily cleaved specific neutral endopeptidase substrates and oxytocin as well as the synthetic elastase substrate, Suc(Ala)3-pNA, yet did not digest native elastin. Using specific inhibitors, the uterus endopeptidase was identified as a metallopeptidase and not a serine protease, having an absolute requirement for zinc and perhaps calcium for maximal activity. The uterus endopeptidase cross-reacted with polyclonal antiserum to kidney microvillar endopeptidase and a monoclonal antibody to common acute lymphocytic leukemia antigen. Immunohistochemical localization of the enzyme in a 17 day pregnant uterus indicated that the enzyme was localized on the smooth muscle bundles of the myometrium and the endometrial epithelium. Total enzyme activity was 25 times higher in the late-term pregnant uterus (17th day of pregnancy) than in the nonpregnant uterus. Enzyme levels dropped rapidly prior to parturition and within 4 days after delivery the enzyme activity had returned to control levels. Inhibition of NEP in uterine strips with phosphoramidon resulted in a marked potentiation of oxytocin-induced contractions. Our results suggest that the uterine endopeptidase may have an important role in regulating uterine smooth muscle cell contraction during the later stages of pregnancy through its action on oxytocin and perhaps other biologically active peptides. 相似文献
67.
This paper concerns an enzymological investigation into a putative canine canalogue of the human autosomal recesive disease primary hyperoxaluria type 1 (alanine:glyoxylate / serine:pyruvate aminotransferase deficiency). The liver and kidney activities of alanine:glyoxylate aminotransferase and seribe:pyruvate aminotransferase in two Tibetan Spaniel pups with familial oxalate nephripathy were markedly reduced when compared with a variety of controls. There were no obvious deficiencies in a number of other enzymes including d-glycerate dehydrogenese / glyoxylate reductase which have been shown previously to be deficient in primary hyperoxaluria type 2. Immunoblotting of liver and kidney homogenates from oxalotic dogs also demonstrated a severe deficiency of immunoreactive alanine:glyoxylate aminotransferase. The developmental expression of alanine:glyoxylate / serine:pyruvate aminotransferase was studied in the livers and kidneys of control dogs. In the liver, enzyme activity and immunoreactive protein were virtually undetectable at 1 day old, but then increased to reach a plateau between 4 and 12 weeks. During this period the activity was similar to that found in normal humanb liver. The enzyme activities and the levels of immunoreactive protein in the kidneys were more erratic, but they appeared to increase up to 8 weeks and then decrease, so that by 36 weeks the levels were similar to those found at 1 day. The data presented in this paper suggest that these oxalotic dogs have a genetic condition that is anlogous, at least enzymologically, to the human disease primary hyperoxaluria type 1. 相似文献
68.
Inhibition of epidermal growth factor-induced DNA synthesis by tyrosine kinase inhibitors 总被引:10,自引:0,他引:10
Kazuo Umezawa Takashi Hori Hirohisa Tajima Masaya Imoto Kunio Isshiki Tomio Takeuchi 《FEBS letters》1990,260(2):201-205
We prepared methyl 2,5-dihydroxycinnamate as a stable analogue of erbstatin, a tyrosine kinase inhibitor. This analogue was about 4 times more stable than erbstatin in calf serum. It inhibited epidermal growth factor receptor-associated tyrosine kinase in vitro with an IC50 of 0.15 μg/ml. It also inhibited in situ autophosphorylation of epidermal growth factor receptor in A431 cells. Methyl 2,5-dihydroxycinnamate was shown to delay the S-phase induction by epidermal growth factor in quiescent normal rat kidney cells, without affecting the total amount ofDNA synthesis. The effect of erbstatin on S-phase induction was smaller, possibly because of its shorter life time. 相似文献
69.
Intrinsic protein phosphorylation was studied in synaptosomal membrane fragments made from cerebral cortex tissue taken from the following species: human (biopsy specimens), ox, rat, rabbit, guinea pig and mouse. Membrane fragments from all species exhibited a qualitatively similar range of protein acceptors phosphorylated by cyclic AMP-dependent protein kinase activity; contrary to a previous report, no evidence for cyclic GMP-dependent protein kinase activity was found in the human material. With the exception of membrane fragments prepared from ox brain, all the preparations exhibited the same range of Ca2+-dependent protein kinase activity. Ox brain obtained from a slaughterhouse yielded membranes containing no Ca2+-dependent protein kinase activity, but this may have been due to unavoidable postmortem losses. 相似文献
70.
S. A. Weiss T. L. Lester S. S. Kalter R. L. Heberling 《In vitro cellular & developmental biology. Plant》1980,16(7):616-628
Summary Chemically defined media SFRE-199-1 for the growth and SFRE-199-2 for the maintenance of primary baboon kidney (Bak) cell
cultures were formulated by supplementing medium M199 with insulin, sodium pyruvate, zinc sulfate, and increasing arginine-HCl,
cysteine, cystine,l-glutamine,l-glutamic acid, glycine, histidine, tyrosine, and glucose to maximally active nontoxic concentrations. For prolonged maintenance
of the cells, physiological pH control, and blocking of excessive lactic acid accumulation in the spent medium of the cell
cultures, it was necessary to supplement the medium containing Earle's balanced salts withd-(+) galactose.
The cells grew and were maintained equally well on glass or polystyrene surfaces. Selenium, when added to growth medium or
substituted for insulin and zinc sulfate, did not stimulate cell growth. Electron microscopy showed that numerous dense particles,
approximately 250 to 400 ? in diameter, with the appearance of glycogen, were found throughout the cytoplasm in the cells
grown in SFRE-199-1 and maintained in SFRE-199-2. Echovirus types 1 to 3, poliovirus types 1 to 3, coxsackievirus types B2,
B4, B5,Herpesvirus hominis type 1, simian herpesvirusH. simiae and SA8, and simian adenovirus SV34 when titrated in primary Bak cells and grown and maintained in SFRE-199-1 and 2, respectively,
developed titers comparable to those obtained in conventionally grown and maintained cells.
This study was supported in part by National Institute of Health Grant RR00361 and World Health Organization Grant V4/181/38.
This laboratory serves as the NIH/WHO Collaborating Center for Reference and Research in Simian Viruses. 相似文献