Twitch activation in Ca2+ -free solutions in the myotomes of the lancelet (Branchiostoma lanceolatum)
Melzer, W.
European Journal of Cell Biology 28(2): 219-225
1982
ISSN/ISBN: 0171-9335 PMID: 7173221 Document Number: 195100
The question of whether a ca2+ influx is necessary to activate twitches in the very thin myotome cells of the lancelet was reinvestigated. Though twitches were blocked in EGTA ethyleneglycol-bis(.beta.-aminoethyl ether)-N,N,N',N'-tetraacetic acid containing Ca2+-free bathing solutions, they reappeared under certain conditions: when the Mg2+ level was lowered, when small amounts of caffeine were added, and when Cl- in the bathing solution was partly replaced by SCN-. In Ca2+-containing solutions, the changes of Mg and Cl increased the twitch height. A Ca2+ release from the intracellular stores is evidently involved in twitch activation, and external Ca2+ modifies the coupling between excitation and Ca2+ release rather than initiating contractile activation.