Premium
Simultaneous recording of intramembrane charge movement components and calcium release in wild‐type and S100A1 −/− muscle fibres
Author(s) -
Prosser Benjamin L.,
HernándezOchoa Erick O.,
Zimmer Danna B.,
Schneider Martin F.
Publication year - 2009
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 - 10.1113/jphysiol.2009.177246
Subject(s) - biophysics , chemistry , egta , voltage clamp , membrane potential , patch clamp , calcium , pipette , electrophysiology , analytical chemistry (journal) , biochemistry , biology , chromatography , neuroscience , receptor , organic chemistry
In the preceding paper, we reported that flexor digitorum brevis (FDB) muscle fibres from S100A1 knock‐out (KO) mice exhibit a selective suppression of the delayed, steeply voltage‐dependent component of intra‐membrane charge movement current termed Q γ . Here, we use 50 μ m of the Ca 2+ indicator fluo‐4 in the whole cell patch clamp pipette, in addition to 20 m m EGTA and other constituents included for the charge movement studies, and calculate the SR Ca 2+ release flux from the fluo‐4 signals during voltage clamp depolarizations. Ca 2+ release flux is decreased in amplitude by the same fraction at all voltages in fibres from S100A1 KO mice compared to fibres from wild‐type (WT) littermates, but unchanged in time course at each pulse membrane potential. There is a strong correlation between the time course and magnitude of release flux and the development of Q γ . The decreased Ca 2+ release in KO fibres is likely to account for the suppression of Q γ in these fibres. Consistent with this interpretation, 4‐chloro‐ m ‐cresol (4–CMC; 100 μ m ) increases the rate of Ca 2+ release and restores Q γ at intermediate depolarizations in fibres from KO mice, but does not increase Ca 2+ release or restore Q γ at large depolarizations. Our findings are consistent with similar activation kinetics for SR Ca 2+ channels in both WT and KO fibres, but decreased Ca 2+ release in the KO fibres possibly due to shorter SR channel open times. The decreased Ca 2+ release at each voltage is insufficient to activate Q γ in fibres lacking S100A1.