| First Author | Prosser BL | Year | 2009 |
| Journal | J Physiol | Volume | 587 |
| Issue | Pt 18 | Pages | 4543-59 |
| PubMed ID | 19651766 | Mgi Jnum | J:176791 |
| Mgi Id | MGI:5292646 | Doi | 10.1113/jphysiol.2009.177246 |
| Citation | Prosser BL, et al. (2009) Simultaneous recording of intramembrane charge movement components and calcium release in wild-type and S100A1-/- muscle fibres. J Physiol 587(Pt 18):4543-59 |
| abstractText | 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(gamma). Here, we use 50 microm of the Ca(2+) indicator fluo-4 in the whole cell patch clamp pipette, in addition to 20 mM 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(gamma). The decreased Ca(2+) release in KO fibres is likely to account for the suppression of Q(gamma) in these fibres. Consistent with this interpretation, 4-chloro-m-cresol (4-CMC; 100 microm) increases the rate of Ca(2+) release and restores Q(gamma) at intermediate depolarizations in fibres from KO mice, but does not increase Ca(2+) release or restore Q(gamma) 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(gamma) in fibres lacking S100A1. |
