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The action potential in Chara : Ca 2+ release from internal stores visualized by Mn 2+ ‐induced quenching of fura‐dextran
Author(s) -
Plieth Christoph,
Sattelmacher Burkhard,
Hansen UlfPeter,
Thiel Gerhard
Publication year - 1998
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1046/j.1365-313x.1998.00019.x
Subject(s) - quenching (fluorescence) , fluorescence , chemistry , biophysics , calcium , chara , analytical chemistry (journal) , vacuole , excited state , membrane , fura 2 , cytoplasm , cytosol , chromatography , biochemistry , biology , physics , quantum mechanics , enzyme , organic chemistry , ecology , nuclear physics
Summary The action potential (AP) in Chara is associated with a transient elevation in the concentration of cytoplasmic‐free Ca 2+ ([Ca 2+ ] cyt ). The quenching properties of the fluorescent Ca 2+ indicator dye fura‐dextran, in combination with Mn 2+ , was used to investigate whether this [Ca 2+ ] cyt transient is due to Ca 2+ release from internal stores or to Ca 2+ influx across the plasma membrane. Adding Mn 2+ to the external medium or pre‐injection of Mn 2+ into the vacuole caused no perceivable quenching of the fura fluorescence, during an AP. This makes it unlikely that Ca 2+ influx across the plasma membrane or the tonoplast contributes significantly to the [Ca 2+ ] cyt transient in an excited cell. When cells were pre‐incubated in external solutions containing Mn 2+ from 25 to 30 mM APs evoked a transient quenching of fura fluorescence in Mn 2+ ‐free solutions. Under these conditions, the quenching must be attributed to an AP‐associated release of Mn 2+ from internal stores. Based on the finding that exposing cells to millimolar concentrations of Mn 2+ caused a progressive quenching of the fura fluorescence in non‐excited cells, it can be assumed that some Mn 2+ enters the cells during pre‐incubation and is loaded into internal stores. During excitation, this stored Mn 2+ is released together with Ca 2+ .