Ionophore A23187: the effect of proton concentration on complex formation with divalent and monovalent cations and the demonstration of potassium(1+) ion transport in mitochondria mediated by A23187

Biochemistry ◽  
1976 ◽  
Vol 15 (5) ◽  
pp. 935-943 ◽  
Author(s):  
Douglas R. Pfeiffer ◽  
Henry A. Lardy
Keyword(s):  
Complex Formation ◽  
Ion Transport ◽  
Ionophore A23187 ◽  
Monovalent Cations ◽  
Proton Concentration ◽  
Transport In Mitochondria

Effects of histamine and histamine receptor antagonists on ion transport in rabbit descending colon

1984 ◽  
Vol 247 (4) ◽  
pp. G411-G418 ◽  
Author(s):  
R. D. McCabe ◽  
P. L. Smith
Keyword(s):  
Ion Transport ◽  
Receptor Antagonist ◽  
Prostaglandin E1 ◽  
Short Circuit ◽  
Bathing Solution ◽  
Ionophore A23187 ◽  
Dependent Manner ◽  
H2 Receptor Antagonist ◽  
Maximal Inhibition ◽  
Descending Colon

The effects of histamine on colonic ion transport were examined in in vitro preparations of rabbit descending colon. Serosal addition of histamine (10(-5) M) produced a transient increase in short-circuit current (Isc) and transepithelial conductance. The Isc response to histamine could be blocked by removing Cl from both bathing solutions, adding furosemide (10(-3) M) to the serosal bathing solution, adding indomethacin to the serosal and mucosal bathing solutions (10(-5) M), or removing Ca from the serosal bathing solution. In addition, the histamine-induced increase in Isc was inhibited in a dose-dependent manner by the H1-receptor antagonist diphenhydramine, with a maximal inhibition at 10(-4) M and a half-maximal inhibition at 3 X 10(-7) M. The H2-receptor antagonist cimetidine (10(-3) M) was without effect on the histamine response. Measurement of unidirectional Na, K, and Cl fluxes revealed that serosal addition of diphenhydramine (10(-3) M) reduced basal Isc due to a decrease in mucosal-to-serosal Na flux. Serosal addition of diphenhydramine (10(-3) M) also inhibited the increase in Isc produced by serosal addition of prostaglandin E1, 8-bromo-cAMP, cholera toxin, or the ionophore A23187. Measurement of unidirectional K and Cl fluxes revealed that prostaglandin E1 alone increased serosal-to-mucosal K and Cl fluxes and reduced the mucosal-to-serosal K flux, thereby increasing net K and Cl secretion. Serosal diphenhydramine (10(-3) M) abolished the changes in Cl fluxes produced by prostaglandin E1 and reduced the magnitude of the changes in K fluxes.(ABSTRACT TRUNCATED AT 250 WORDS)

Ion transport mediated by copolymers composed of polyoxyethylene and polyoxypropylene

1988 ◽  
Vol 254 (1) ◽  
pp. C20-C26 ◽  
Author(s):  
T. P. Atkinson ◽  
J. O. Bullock ◽  
T. F. Smith ◽  
R. E. Mullins ◽  
R. L. Hunter
Keyword(s):  
Ion Transport ◽  
Lipid Bilayers ◽  
Practical Interest ◽  
Water Soluble ◽  
Planar Lipid Bilayers ◽  
Monovalent Cations ◽  
Transport Activity ◽  
Experimental Systems ◽  
Surface Active Agents ◽  
Surface Active

Block copolymers composed of polyoxyethylene and polyoxypropylene were found to increase the influx of Na+ and the efflux of K+ from human erythrocytes. They were, however, ineffective at promoting the transport of Ca2+. The size of the ion fluxes induced by the copolymers correlated with their efficacy in stimulating inflammation. These compounds were also found to induce conductance increases in planar lipid bilayers in a nonvoltage dependent and nonstepwise manner. In both experimental systems, ion transport was facilitated only under temperature and ionic-strength conditions in which the polymers form aggregates in aqueous solution. In neither system did the concentration dependence of transport activity exhibit a pronounced cooperativity. These observations are consistent with the view that aqueous monomers of these surface active agents partition into the membrane, where they facilitate the conductive movement of monovalent cations by means of a carrier type mechanism. As a novel class of ionophores, these substances are of practical interest because they can be water soluble and are potentially reversible.

Studies on the association of the α and β2 subunits of the tryptophan synthase of Bacillus subtilis

1981 ◽  
Vol 27 (6) ◽  
pp. 604-611
Author(s):  
Sallie O. Hoch ◽  
Katrin Soldau
Keyword(s):  
Bacillus Subtilis ◽  
Complex Formation ◽  
Gel Filtration ◽  
Enzymatic Activities ◽  
Tryptophan Synthase ◽  
Monovalent Cations ◽  
C Complex ◽  
The Individual

Studies using Sephadex gel filtration indicated that the α and β2 components of the Bacillus subtilis tryptophan synthase associate to form complexes under the appropriate conditions of buffer, pH, and temperature. Monovalent cations, glycerol, and the cofactor, pyridoxal-5′-phosphate, were required to maintain an active β2 component, and in turn, affected the association of the α and β2 components. Under conditions that stabilized the individual components during their purification, the affinity of the subunits for each other was weak. Under the same buffer conditions, but at the higher pH of 7.8 at which the enzymatic activities are assayed, the individual components readily associated. The substrate serine appeared to affect complex formation but there was no effect from the indole moiety. When the temperature was raised from 4 to 22–25 °C, complex formation was observed at both pH 6.6 and 7.8. The results of these experiments are consistent with the formation of αβ2 and α2β2 species as the associated tryptophan synthase complexes of B. subtilis.

Dantrolene and basal ileal sodium and chloride transport: involvement of calcium stores

1983 ◽  
Vol 245 (6) ◽  
pp. G780-G785
Author(s):  
M. Donowitz ◽  
S. Cusolito ◽  
L. Battisti ◽  
G. W. Sharp
Keyword(s):  
Ion Transport ◽  
Intracellular Calcium ◽  
Chloride Transport ◽  
Short Circuit ◽  
Ussing Chamber ◽  
Short Circuit Current ◽  
Calcium Stores ◽  
Ionophore A23187 ◽  
Rabbit Ileum ◽  
Intracellular Calcium Stores

The effect of dantrolene on active ion transport in rabbit ileum was determined using the Ussing chamber short-circuiting technique. Dantrolene prevents the release of calcium from intracellular stores in skeletal muscle and was used to probe the role of intracellular calcium stores in intestinal ion transport. A saturated solution of dantrolene (approx 25 microM) decreased ileal short-circuit current and potential difference, increased conductance and mucosal-to-serosal and net Na and Cl fluxes, but did not alter serosal-to-mucosal Na and Cl fluxes. The dantrolene stimulation of active Na and Cl absorption was specific since it did not alter glucose-dependent Na absorption, transport changes caused by Ca2+ ionophore A23187, or the increase in short-circuit current caused by dibutyryl cAMP or theophylline. These effects were associated with an increase in total ileal calcium content and a decreased rate of 45Ca2+ efflux without any change in 45Ca2+ influx from the serosal or mucosal surfaces. These findings are consistent with an effect of dantrolene to stimulate active ileal Na and Cl absorption by a mechanism involving lowered cytosol Ca2+ levels and compatible with trapping calcium in intracellular stores. It thus appears as if intracellular calcium stores have an important role in the control of basal ion transport in the intestine.

scholarly journals Phenotype of a Mechanosensitive Channel Mutant, mid-1, in a Filamentous Fungus, Neurospora crassa

2008 ◽  
Vol 7 (4) ◽  
pp. 647-655 ◽  
Author(s):  
Roger R. Lew ◽  
Zohaib Abbas ◽  
Marinela I. Anderca ◽  
Stephen J. Free
Keyword(s):  
Ion Transport ◽  
Neurospora Crassa ◽  
Carbon Sources ◽  
Homologous Gene ◽  
Ionophore A23187 ◽  
Wild Type ◽  
Knockout Mutant ◽  
Lower Growth ◽  
Filamentous Ascomycete ◽  
Energy Dependent

ABSTRACT In the yeast Saccharomyces cerevisiae, the MID1 (mating-induced death) gene encodes a stretch-activated channel which is required for successful mating; the mutant phenotype is rescued by elevated extracellular calcium. Homologs of the MID1 gene are found in fungi that are morphologically complex compared to yeast, both Basidiomycetes and Ascomycetes. We explored the phenotype of a mid-1 knockout mutant in the filamentous ascomycete Neurospora crassa. The mutant exhibits lower growth vigor than the wild type (which is not rescued by replete calcium) and mates successfully. Thus, the role of the MID-1 protein differs from that of the homologous gene product in yeast. Hyphal cytology, growth on diverse carbon sources, turgor regulation, and circadian rhythms of the mid-1 mutant are all similar to those of the wild type. However, basal turgor is lower than wild type, as is the activity of the plasma membrane H+-ATPase (measured by cyanide [CN−]-induced depolarization of the energy-dependent component of the membrane potential). In addition, the mutant is unable to grow at low extracellular Ca2+ levels or when cytoplasmic Ca2+ is elevated with the Ca2+ ionophore A23187. We conclude that the MID-1 protein plays a role in regulation of ion transport via Ca2+ homeostasis and signaling. In the absence of normal ion transport activity, the mutant exhibits poorer growth.

Inhibition of cation efflux by antioxidants during oscillatory ion transport in mitochondria

FEBS Letters ◽  
1979 ◽  
Vol 107 (1) ◽  
pp. 151-154 ◽  
Author(s):  
Wolfgang Augustin ◽  
Frank Gellerich ◽  
Ingrid Wiswedel ◽  
Yuri Evtodienko ◽  
Valeri Zinchenko
Keyword(s):  
Ion Transport ◽  
Transport In Mitochondria
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