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Phosphate ion channels in sarcoplasmic reticulum of rabbit skeletal muscle
Author(s) -
Laver Derek R.,
Lenz Gerlinde K. E.,
Dulhunty Angela F.
Publication year - 2001
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2001.t01-1-00715.x
Subject(s) - chemistry , dids , conductance , biophysics , divalent , chloride channel , skeletal muscle , ion channel , ion transporter , endoplasmic reticulum , phosphate , lipid bilayer , biochemistry , membrane , anatomy , biology , receptor , mathematics , organic chemistry , combinatorics
1 Phosphate ions (P i ) enter intracellular Ca 2+ stores and precipitate Ca 2+ . Since transport pathways for P i across the membrane of intracellular calcium stores have not been identified and anion channels could provide such a pathway, we have examined the P i conductance of single anion channels from the sarcoplasmic reticulum (SR) of rabbit skeletal muscle using the lipid bilayer technique. 2 Two anion channels in skeletal muscle SR, the small conductance (SCl) and big conductance (BCl) chloride channels, were both found to have a P i conductance of 10 pS in 50 m m P i . The SCl channel is a divalent anion channel which can pass HPO 4 2− as well as SO 4 2− (60 pS in 100 m m free SO 4 2− ). The BCl channel is primarily a monovalent anion channel. The SCl and BCl channels are permeable to a number of small monovalent anions, showing minor selectivity between Cl − , I − and Br − (Cl − > I − > Br − ) and relative impermeability to cations and large polyatomic anions (Cs + , Na + , choline + , Tris + , Hepes − and CH 3 O 3 S − ). 3 The P i conductance of SCl and BCl channels suggests that both channel types could sustain the observed P i fluxes across the SR membrane. Comparison of the blocking effects of the phosphonocarboxylic acids, ATP and DIDS, on the anion channels with their effects on P i transport suggests that the SCl channel is the more likely candidate for the SR P i transport mechanism. 4 The SCl channel, with previously unknown function, provides a regulated pathway for P i across the SR membrane which would promote P i entry and thereby changes in the rapidly releasable Ca 2+ store during onset and recovery from muscle fatigue. Anion channels may provide a pathway for P i movement into and out of Ca 2+ stores in general.