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: Transport of N1-methylnicotinamide across brush border membrane vesicles from rabbit kidney.
    Author: Wright SH.
    Journal: Am J Physiol; 1985 Dec; 249(6 Pt 2):F903-11. PubMed ID: 2933962.
    Abstract:
    A preparation of isolated brush border membranes from the rabbit renal cortex was used to examine the characteristics of N1-methylnicotinamide (NMN) transport in the kidney. Transport was independent of the presence of Na+ under Na+ equilibrium conditions. However, outwardly directed Na+ gradients stimulated NMN uptake, whereas inwardly directed Na+ gradients inhibited NMN uptake. Transport appeared to involve two parallel processes: one saturable with a Jmax of 5 nmol X mg protein-1 X min-1 and an apparent Kt of 0.6 mM, and a second that behaved like passive diffusion. Countertransport of NMN was observed when vesicles were preloaded with either NMN or another organic cation, tetraethylammonium (TEA). TEA and several structural analogues, as well as a wide variety of other organic cations and bases, were effective inhibitors of NMN uptake, though nicotinamide and p-aminohippuric acid did not interact with the uptake process. Outwardly directed proton gradients (pH 6.0 in, 7.6 out) stimulated transport, suggesting that NMN uptake may involve a countertransport of H+. The electrical potential difference across the vesicle membrane was manipulated using gradients of the permeant organic ion thiocyanate (SCN-); an outwardly directed gradient of SCN- (i.e., a depolarizing condition) stimulated uptake and produced a transient accumulation of NMN above that noted at equilibrium, whereas an inwardly directed SCN- gradient inhibited uptake of NMN. The data can be explained by postulating the presence of an electrogenic NMN+-H+ antiporter in the rabbit luminal membrane that could play a role in organic cation secretion.
    [Abstract] [Full Text] [Related] [New Search]