摘要:

Recent studies indicate that a gastric-like HK-ATPase activity could account for electroneutral H-K exchange in both kidney and colon. To determine the molecular mechanism responsible for this activity, we used antibodies (HK9 and HKB) directed against two distinct epitopes of the gastric HK-ATPase in western blot analysis of kidney and distal colon. A protein of molecular weight similar to that of the gastric HK-ATPase was identified by one antiserum (HK9) and not by the other (HKB). The protein identified by HK9 was found to be expressed in greater abundance in the inner medulla than in cortex and outer medulla. This result suggests that, a protein similar, but not identical, to gastric HK-ATPase may participate in proton secretion and potassium absorption in the inner medulla. We conclude that a protein that is part of a molecular family of gastric HK-ATPase is present in kidney and distal colon.

ISSN:1094-9313    

DOI:10.1159/000154735

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

Malignant hyperthermia (MH) is an anesthetic-induced, life-threatening hypermetabolic state occurring in genetically predisposed pigs, dogs and humans. It is widely believed that MH is caused by an abnormal elevation of myoplasmic calcium, induced by the action of certain anesthetics. Five MH-susceptible (MHS) and 5 MH-nonsusceptible (MHN) pigs were biopsied from the longissimus dorsi muscle for isolation of sarcoplasmic reticulum membrane vesicles. These vesicles were fused into a planar lipid bilayer, and the system selectively measured conductance of cesium ions by the ryanodine-sensitive calcium release channel. Single channel events were recorded in the absence and presence of the anesthetic halothane; these records were subsequently analyzed to assess the gating and conductance properties. In the absence of halothane, calcium release channels from MHS muscle had average conductance values (447 ± 10 pS) that did not differ from those of MHN muscle (439 ± 28 pS). Average open life time value for MHS channels (0.55 ± 0.12 ms) was greater (p < 0.01) than it was for MHN channels (0.28 ± 0.07 ms). Average closed dwell time for MHS channels (4.44 ± 1.6 ms) did not differ from that in MHN channels (7.33 ± 3.8 ms). Halothane affected all MHS channels, whereas the MHN channels were not affected by halothane concentrations up to 68 µM. Halothane increased the average open state dwell time of MHS channels from 0.552 ± 0.12 ms in the controls to 0.808 ± 0.15 ms in the presence of 16 µM halothane and was without effect on open dwell time of MHN channels. Halothane did not significantly increase open state probability in MHS or MHN channels. Halothane produced increases (p < 0.05) in single channel conductance of the MHS channels but not in the MHN channels. The abnormal open state lifetimes of MHS channels in the absence of halothane may reflect the effect of the mutation on normal channel function, whereas the abnormal effects of halothane on MHS channels are consistent with a theory that MH is caused by an elevation of myoplasmic calcium induced by certain an

ISSN:1094-9313    

DOI:10.1159/000154736

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

Heat-stable toxin (STa) increases cyclic GMP (cGMP) in isolated intestinal cells and in T84 cells, a colonic secretory cell line. Whole-cell current recordings from patch clamp experiments show identical properties for currents activated by either STa or the cystic fibrosis transmembrane conductance regulator (CFTR) channel. STa-activated currents display a linear current-voltage relationship and a relative permeability sequence of Br > Cl > I. STa or 8-Br-cGMP-activated currents remain when 20 µM Walsh inhibitor, a blocker of protein kinase A (PKA), is added in the pipette, suggesting that cGMP-dependent protein kinase (PKG) activates the currents. Intracellular addition of Rp-8-Br-cGMP, an agent that activates PKGII and inhibits PKGI and PKA, causes induction of a chloride conductance identical to that stimulated by STa. We conclude that STa activates CFTR by phosphorylation with cGMP-dependent protein kinase

ISSN:1094-9313    

DOI:10.1159/000154737

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

A soluble carbohydrate-binding protein with galactoside-binding properties (CBP14) was isolated from liver nuclei of adult rats. Proteins were extracted from membrane-depleted nuclei; they contained 3 major fractions (Mr 43,000, 14,000 and 10,000) which reacted with antibodies raised against human placental β-galactoside-binding lectin (HP 14) as well as with asialofetuin (ASF). Enrichment (72- to 143-fold) of CBP14 was carried out by affinity chromatography, using anti-HP 14 antibodies and ASF as consequent ligands. CBP14 retained by affinity column chromatography was characterized by the molecular mass, haemagglutinating activity and immuno-chemical cross-reactivity. By fluorescence technique using fluorescein-labelled neoglycoprotein (carrying lactose) as a probe, lactose-binding protein(s), e.g. the CBP14 described here, can be detected in a homogeneous staining pattern within the entire nucleus of CV-1 cells in the stationary phase of the cells. In case of logarithmically proliferating cells the lactose-binding protein(s) are arranged in a spot-like pattern along the rims of the cell nuclei. The putative ligand for the CBP14 is associated with the nuclear surface, irrespective of the proliferation state of the cells

ISSN:1094-9313    

DOI:10.1159/000154738

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

Artificially-generated O2 radicals have been introduced into rat Langendorff hearts by perfusion with either menadione or H2O2. Menadione (0.2 mM) caused the release of creatine kinase (CK), but only when previously activated by Ca2+-free perfusion. Release was inhibited at 28°C or by perfusion under N2. Menadione still caused severe ultrastructural damage when no CK release occurred, i.e. in the presence of Ca2+o. Menadione can also directly inhibit the CK release mechanism. H2O2 (0.3 mM) caused ultrastructural damage, but CK release was again completely dependent on Ca2+-free priming. Dimethylthiourea afforded substantial protection, suggesting that OH radicals are generated by H2O2. It is concluded that Ca2+-free perfusion causes a temperature-sensitive activation of the CK release system; menadione or H2O2 generate O2 radicals that cause the release of Ca2+ intracellularly which triggers myofilament damage directly and which also acts synergistically with the activated damage system to effect CK release. The results confirm that myofilament damage and CK release are independent damage pathways and that the CK release mechanism requires a dual activation of Ca2+ depletion plus a rise in [Ca2+]i

ISSN:1094-9313    

DOI:10.1159/000154739

出版商:S. Karger AG    

年代:1995

数据来源: Karger

ISSN:1094-9313    

DOI:10.1159/000154740

出版商:S. Karger AG    

年代:1995

数据来源: Karger

ISSN:1094-9313    

DOI:10.1159/000154741

出版商:S. Karger AG    

年代:1995

数据来源: Karger

ISSN:1094-9313    

DOI:10.1159/000154742

出版商:S. Karger AG    

年代:1995

数据来源: Karger