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XB-ART-23103
J Muscle Res Cell Motil 1992 Dec 01;136:630-4. doi: 10.1007/BF01738252.
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Relaxation rate of intact striated muscle fibres after flash photolysis of a caged calcium chelator (diazo-2).

Lännergren J , Arner A .


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Single twitch fibres from lumbrical muscles of Xenopus have been loaded with the photolysable calcium-chelator diazo-2 by incubation in Ringer solution containing the membrane permeable acetoxymethyl ester (AM) form of diazo-2. Incubation caused a progressive slowing of tetanus rise and relaxation which is ascribed to calcium-buffering by unphotolyzed diazo-2 (Kd = 2.2 microM). After incubation, exposure to a brief UV flash caused a three to four fold increase in the rate of tension fall. A flash given 16-18 ms after the last tetanic stimulus (at 22-24 degrees C) resulted in 10% increase in relaxation rate compared with the control before incubation. A much bigger effect was observed when a flash was given half-way into the slow phase, where an 1.8-1.9-fold increase in relaxation rate, above the preincubation slope, was observed. It is concluded that rapid lowering of [Ca]i, and hence more rapid removal of Ca2+ from troponin, speeds up relaxation, indicating that calcium translocation is the major determinant of the rate of tension fall during the isometric phase of relaxation.

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Species referenced: Xenopus laevis
Genes referenced: adm

References [+] :
Blinks, Calcium transients in isolated amphibian skeletal muscle fibres: detection with aequorin. 1978, Pubmed, Xenbase