About: The dependence of ascorbate uptake on external cations was studied in primary cultures of rat cerebral astrocytes. Initial rates of ascorbate uptake were diminished by lowering the external concentrations of either Ca(2+) or Na(+). The Na(+)-dependence of astroglial ascorbate uptake gave Hill coefficients of approximately 2, consistent with a Na(+)-ascorbate cotransport system having stoichiometry of 2 Na(+)∶1 ascorbate anion. Raising external K(+) concentration incrementally from 5.4 to 100 mM, so as to depolarize the plasma membrane, decreased the initial rate of ascorbate uptake, with the degree of inhibition depending on the level of K(+). The depolarizing ionophores gramicidin and nystatin slowed ascorbate uptake by astrocytes incubated in 5.4 mM K(+); whereas, the nondepolarizing ionophore valinomycin did not. Qualitatively similar results were obtained whether or not astrocytes were pretreated with dibutyryl cyclic AMP (0.25 mM for 2 weeks) to induce stellation. These data are consistent with the existence of an electrogenic Na(+)-ascorbate cotransport system through which the rate of ascorbate uptake is modulated by endogenous agents, such as K(+), that alter astroglial membrane potential.   Goto Sponge  NotDistinct  Permalink

An Entity of Type : fabio:Abstract, within Data Space : wasabi.inria.fr associated with source document(s)

AttributesValues
type
value
  • The dependence of ascorbate uptake on external cations was studied in primary cultures of rat cerebral astrocytes. Initial rates of ascorbate uptake were diminished by lowering the external concentrations of either Ca(2+) or Na(+). The Na(+)-dependence of astroglial ascorbate uptake gave Hill coefficients of approximately 2, consistent with a Na(+)-ascorbate cotransport system having stoichiometry of 2 Na(+)∶1 ascorbate anion. Raising external K(+) concentration incrementally from 5.4 to 100 mM, so as to depolarize the plasma membrane, decreased the initial rate of ascorbate uptake, with the degree of inhibition depending on the level of K(+). The depolarizing ionophores gramicidin and nystatin slowed ascorbate uptake by astrocytes incubated in 5.4 mM K(+); whereas, the nondepolarizing ionophore valinomycin did not. Qualitatively similar results were obtained whether or not astrocytes were pretreated with dibutyryl cyclic AMP (0.25 mM for 2 weeks) to induce stellation. These data are consistent with the existence of an electrogenic Na(+)-ascorbate cotransport system through which the rate of ascorbate uptake is modulated by endogenous agents, such as K(+), that alter astroglial membrane potential.
subject
  • Vitamin C
  • Membrane biology
  • Physical chemistry
part of
is abstract of
is hasSource of
Faceted Search & Find service v1.13.91 as of Mar 24 2020


Alternative Linked Data Documents: Sponger | ODE     Content Formats:       RDF       ODATA       Microdata      About   
This material is Open Knowledge   W3C Semantic Web Technology [RDF Data]
OpenLink Virtuoso version 07.20.3229 as of Jul 10 2020, on Linux (x86_64-pc-linux-gnu), Single-Server Edition (94 GB total memory)
Data on this page belongs to its respective rights holders.
Virtuoso Faceted Browser Copyright © 2009-2025 OpenLink Software