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: Block of calcium-activated potassium channels in mammalian arterial myocytes by tetraethylammonium ions.
    Author: Langton PD, Nelson MT, Huang Y, Standen NB.
    Journal: Am J Physiol; 1991 Mar; 260(3 Pt 2):H927-34. PubMed ID: 1900393.
    Abstract:
    The effects of tetraethylammonium ions (TEA+) and tetrapentylammonium ions (TPeA+) on Ca2(+) -activated K+ (KCa) channels were studied in membrane patches from mesenteric arterial myocytes. External TEA+ produced a flickery block. The concentration dependence for reduction in mean unitary current was consistent with 1:1 binding, with dissociation constants (Kd) in rat and rabbit of 196 and 159 microM at 0 mV, and the block was weakly voltage dependent. Rate constants for blocking and unblocking were 380 mM-1.ms-1 and 73 ms-1, respectively. In patches containing several channels TEA+ reduced average current to the same extent as mean unitary current, implying that TEA+ block is independent of the channel state. Block was unaffected by raising external K+ to 120 mM. External TPeA+ blocked with slower kinetics and lower affinity than TEA+ (Kd, 1.49 mM). The sulfonylurea glibenclamide (10-100 microM), the hyperpolarizing vasodilator cromakalim (5 microM), and internal ATP (1 mM) were without effect on channel activity. We conclude that TEA+ is a relatively effective blocker of single KCa channels of arterial smooth muscle and should block macroscopic currents equally well, whereas external TPeA+ is about eight times less effective.
    [Abstract] [Full Text] [Related] [New Search]