These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Calcium transport and monovalent cation and proton fluxes in sarcoplasmic reticulum vesicles.
    Author: Meissner G.
    Journal: J Biol Chem; 1981 Jan 25; 256(2):636-43. PubMed ID: 7451464.
    Abstract:
    ATP-dependent Ca2+ uptake by rabbit skeletal muscle sarcoplasmic reticulum vesicles has been studied in the presence and absence of artificially generated pH gradients and membrane potentials. H+ and K+ diffusion potentials were generated via the H+ and K,Na channels of sarcoplasmic reticulum by transfer of vesicles from low to high pH, or from high to low K+. Membrane potentials were measured using the voltage-sensitive fluorescent dye 3,3'-dipentyl-2,2'-oxacarbocyanine. The initial rate of Ca2+ uptake was found to be increased in the presence of a pH gradient and membrane potential (negative inside). In turn, the rates of decay of K+- or H+-induced membrane potentials were accelerated during Ca2+ transport, suggesting that active Ca2+ uptake stimulated the release of K+ and H+ from the vesicles. The ratio of K+ (or H+) release to Ca2+ transport was near two. Release of K+ did not appear to be directly catalyzed by the Ca2+-ATPase. Evidence against a directly coupled ATP-mediated 2 K+-Ca2+ or K+-Ca2+ exchange reaction was that (i) similar results were obtained when K+ was substituted by Na+ or by organic cations which could rapidly permeate through the channel of K+,Na+-permeable vesicles and (ii) Ca2+ transport did not result in an equivalent release of 86Rb+ or 22Na+ from K+,Na+-impermeable vesicles. These studies are in support of an electrogenic Ca2+ transport system in sarcoplasmic reticulum. The results further suggest that during Ca2+ transport development of a membrane potential (positive inside) is likely nullified by the countermovement of the permeant cations K+, Na+, and H+.
    [Abstract] [Full Text] [Related] [New Search]