Measurement of free Ca2+ changes and total Ca2+ release in a single striated muscle fibre using the fluorescent indicator quin 2.
The fluorescent Ca2+ indicator, quin 2, has been used in isolated striated muscle fibres. There is a distinct quin 2 fluorescence peak at lambda 500 nm upon excitation at lambda 339 nm after axial injection of the potassium salt of quin 2, pH 7.1. Single voltage-clamp or current clamp electrical stimulation resulted in a distinct transient change in the fluorescence at lambda 500 nm which was not observed at lambda 400 nm, the peak of the fibre autofluorescence. Ca2+ buffering is marked at high quin 2 concentrations (greater than or equal to 400 microM) producing a slow decay of force and fluorescence. At lower concentrations (8-30 microM) of quin, the decay of force is within the range observed in non-injected control fibres. A Kd of 457 nM at 5 mM free Mg2+ suggests an upper resting free Ca2+ concentration of 310 nM at 12 degrees C.
D000634:Aminoquinolines; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D004558:Electric Stimulation; D005456:Fluorescent Dyes; D066298:In Vitro Techniques; D009132:Muscles / Q000378:metabolism*; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D001468:Thoracica / Q000378:metabolism
D000634:Aminoquinolines; D005456:Fluorescent Dyes; C035739:Quin2; D002118:Calcium