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41.
Adolf Dörge Franz X. Beck Roger Rick Wolfram Nagel Klaus Thurau 《Pflügers Archiv : European journal of physiology》1990,416(3):335-338
The role of mitochondria-rich cells (MR cells) in transepithelial Na transport was investigated by determining electrolyte concentrations and Rb uptake in individual cells of frog skin epithelium using electron microprobe analysis. Measurements were performed under control conditions and after blocking the transepithelial Na transport with amiloride. Under control conditions, Na and Cl concentrations of MR cells scattered much more than those of principal cells and ranged from a few up to more than 30 mmol/kg wet weight. Rb uptake from the basal side into individual MR cells also showed a large variation and was, on the average, much less pronounced than into the principal cells. In principal cells, amiloride reduced the Na concentration and Rb accumulation. In contrast, no effect was observed upon electrolyte concentration and Rb uptake of MR cells. Rb uptake was correlated to the Na concentration of MR cells both under control conditions and after amiloride. It is concluded that, in contrast to the principal cells, MR cells are not involved in amiloride-sensitive transepithelial Na transport and that their Na/K-pump activity is very low. 相似文献
42.
F. Jaisser J. D. Horisberger B. C. Rossier 《Pflügers Archiv : European journal of physiology》1993,425(5-6):446-452
The cortical collecting tubule (CCT) of the mammalian kidney reabsorbs sodium and potassium, processes that are mediated by Na/K-ATPase and H/K-ATPase. CCT is also an important site for proton secretion, which is driven, in part, by H/K-ATPase. Na/K-ATPase and H/K-ATPase are members of the ion-motive P-ATPase gene family. They are closely related plasma membrane proteins which consist of heterodimers. The urinary bladder of the toad Bufo marinus is the amphibian counterpart of mammalian CCT. We have previously characterized a ouabain-resistant Na/K-ATPase [see ref. 17], from TBM cells, a clonal cell line derived from the toad bladder, which expresses transepithelial sodium transport. In the present study, we report the primary sequence and functional expression of a novel subunit (
bladder=
bl) isolated from a toad bladder epithelial cell cDNA library. The deduced polypeptide is 299 amino acids in length and has a predicted molecular mass of 33 kDa. The
bl protein exhibits 35% amino acid identity to the previously characterized
1 of B. marinus Na/K-ATPase and 39% identity with
3 of B. marinus Na/K-ATPase. It shares 38% identity with the mammalian gastric H/K-ATPase and 52% with the mammalian
2 Na/K-ATPase. Northern blot analysis shows that a 1.4×103-base mRNA is expressed at a high level in bladder epithelial cells and eye and at a trace level in kidney; it is not detectable in significant amounts in the stomach, colon and small intestine. The
bl subunit can associate with the
1 subunit of B. marinus Na/K-ATPase to form a functional sodium pump in the Xenopus laevis oocyte. Our data indicate that, in addition to the known
1 and
3 isoforms, a third distinct isoform of the subunit is present in the bladder epithelium. This new isoform could be functionally associated with subunits of either Na/K- or H/K-ATPase. 相似文献
43.
44.
K.-M. Zhang Ping Hu Shang-Wu Wang Leon D. Wright Andrew S. Wechsler John A. Spratt F. N. Briggs 《Pflügers Archiv : European journal of physiology》1997,433(6):766-772
Using an immunohistochemical double-labeling technique, we observed that different isoforms of sarcoplasmic reticulum Ca-ATPase
are co-expressed in single fibers of canine fast-twitch skeletal muscles stimulated chronically at low frequency. By 7 days
of neuromuscular stimulation, the population of hybrid fibers expressing both SERCA1 and SERCA2a [fast- and slow-twitch isoforms
of sarco(endo)plasmic reticulum Ca2+-ATPase] had increased from 1.5% to 9.2% of fibers. By 14 days of stimulation 90% of the pure fast-twitch fibers (expressing
only SERCA1) were replaced by hybrid fibers. An additional 28 days of stimulation caused all fast-twitch fibers to express
SERCA2a at the same level as found in nonstimulated slow-twitch fibers (expressing only SERCA2a). At this time, one-half of
the previously hybrid fibers had become pure slow-twitch fibers. The remaining one-half of the hybrid fibers expressed SERCA1
at a very low level. Extending stimulation to 70 days did not further change the percentage of fibers that were slow-twitch
or hybrid. Immunoblot studies at the whole-muscle level confirmed that changes in SERCA expression at 42 days of neuromuscular
stimulation were complete. Immunohistochemical analysis of longitudinal sections of muscle showed that the changes in SERCA
protein were uniform along the length of the muscle fiber, indicating that nuclei along its length responded equally to chronic
stimulation.
Received: 12 November 1996 / Received after revision and accepted: 16 December 1996 相似文献
45.
46.
H. Ochiai N. Hishiyama K. Higa K. Koyama M. Seita H. Fujise 《Comparative clinical pathology》2007,16(1):61-63
The cation transport and regulatory volume decrease (RVD) were investigated in the red blood cells (RBCs) of northern fur
seals (Callorhinus ursinus). Extracellular Ca-dependent Na efflux was increased to threefold by hypotonicity. K–Cl cotransport activity was not detected
by hypotonic medium, but measured only by nitrite or N-ethylmaleimide stimulation. RBCs were restored to their original volume after being swollen in hypoosmotic medium with Ca,
though this recovery was inhibited by the addition of quinidine. Based on these results, Na/Ca exchange transporter played
the major role in the regulatory volume decrease in the RBCs of northern fur seals.
H. Fujise has passed away. 相似文献
47.
Giorgio Torelli Eloisa Milla Leonard I. Kleinman Alide Faelli 《Pflügers Archiv : European journal of physiology》1973,342(3):219-230
Summary The relationship between sodium reabsorption and oxygen consumption was studied in an isolated rabbit kidney preparation perfused with blood at 37, 28 and 19° C. When the temperature was lowered from 37° C to 28° C and to 19°C the rate of oxygen consumption and of the maximal P.A.H. excretion (Tm P.A.H.) decreased more than that of sodium reabsorption.TheQ
10 for sodium reabsorption is about 1.8, while that for maximal P.A.H. excretion is 2.5. Some hypothesis on the possible mechanisms of the lowQ
10 of the Na+ reabsorption are forwarded.Preliminary reports have been published [Boll. Soc. Ital. Biol. Sper.43, 1019–1023 (1966) and44, 1784–1787 (1967);45, 860–862 (1969) and45, 863–865 (1969)]. 相似文献
48.
Xiao B Jing C Kelly G Walker PA Muskett FW Frenkiel TA Martin SR Sarma K Reinberg D Gamblin SJ Wilson JR 《Genes & development》2005,19(12):1444-1454
Methylation of lysine residues of histones is an important epigenetic mark that correlates with functionally distinct regions of chromatin. We present here the crystal structure of a ternary complex of the enzyme Pr-Set7 (also known as Set8) that methylates Lys 20 of histone H4 (H4-K20). We show that the enzyme is exclusively a mono-methylase and is therefore responsible for a signaling role quite distinct from that established by other enzymes that target this histone residue. We provide evidence from NMR for the C-flanking domains of SET proteins becoming ordered upon addition of AdoMet cofactor and develop a model for the catalytic cycle of these enzymes. The crystal structure reveals the basis of the specificity of the enzyme for H4-K20 because a histidine residue within the substrate, close to the target lysine, is required for completion of the active site. We also show how a highly variable component of the SET domain is responsible for many of the enzymes' interactions with its target histone peptide and probably also how this part of the structure ensures that Pr-Set7 is nucleosome specific. 相似文献
49.
Na+, K+-ATPase in renal epithelial cells plays an important role in the regulation of Na+ balance, extracellular volume and blood pressure. The function of renal Na+, K+-ATPase in Dahl salt-sensitive (DS) rats, an animal model for salt-sensitive hypertension, and Dahl salt-resistant (DR) rats has been studied. In Na+, K+-ATPase partially purified from renal cortex, affinities and the Hill coefficients for Na+ and K+ activation were similar in DS and DR rats. Only one component of low ouabain affinity site was found in both strains, indicating the presence of the al isoform. Protein kinase C and cAMP-dependent protein kinase phosphorylated Na+, K+-ATPase α subunit in DS and DR rats, and the phosphorylation by protein kinase C was associated with an inhibition of enzyme activity. The kinetic parameters for K+ activation were also studied in a preparation of basolateral membranes and were found to be similar in DS and DR rats. In a preparation of cortical tubule cells, Na+, K+-ATPase activity was determined as ouabain-sensitive oxygen consumption (OS Qo2). Maximal OS Qo2, measured in Na+ loaded cells, was the same in DS and DR rats. The K06 for K+ was significantly lower in DS than DR rats (0.163 ±0.042 vs. 0.447 + 0.061 mM, P < 0.05), indicating that factors regulating Na+, K+-ATPase activity in intact cells are altered in DS rats. Kinetic parameters for Na+ activation in cells were the same in both strains. In summary, the function of renal Na+, K+-ATPase molecule is not altered in DS rats. The intracellular systems that regulate renal Na+, K+-ATPase activity might be different in DS and DR rats. 相似文献
50.
654—2对家兔红细胞膜Na^+—K^+—ATPase活性及血浆LPO含量的影响 总被引:1,自引:0,他引:1
日本大耳兔9只,其中6~8月龄5只,2~2.5年龄4只。均喂以2%654-2溶液1ml/天(即20mg)共43天。结果不分年龄统计,LPO含最下降0.827±1.048 nmol/ml(P<0.05)。Na~+-K~+-ATPase活性增加0.057±0.074μmol Pi/mg pro/hr(P<0.05)。认为654-2可能有抗衰老作用,并与普鲁卡因比较,讨论了其降低LPO的可能途径。 相似文献