Click here to close
Hello! We notice that you are using Internet Explorer, which is not supported by Xenbase and may cause the site to display incorrectly.
We suggest using a current version of Chrome,
FireFox, or Safari.
Slowing of relaxation and [Ca2+]i during prolonged tetanic stimulation of single fibres from Xenopus skeletal muscle.
Westerblad H
,
Allen DG
.
???displayArticle.abstract???
1. Parvalbumin (PA) has been proposed to take up Ca2+ and enhance skeletal muscle relaxation in brief contractions; as the duration of the contraction is increased, PA will become saturated with Ca2+ and no longer contribute to relaxation which therefore will be slowed. The rate of Ca2+ loading of PA is determined by the Mg2+ off rate (about 4 s-1 at 22 degrees C). In the present study we produced prolonged tetani in intact, single fibres of Xenopus frogs while measuring force and the free myoplasmic [Ca2+] ([Ca2+]i) with indo-1. 2. Mean rate constants of slowing of force relaxation with increasing tetanus duration ranged between 3.2 and 4.8 s-1, thus, similar to the Mg2+ off rate of PA. 3. The amplitude of the tail of [Ca2+]i after tetani increased with tetanus duration. This increase developed with a rate constant similar to the Mg2+ off rate of PA 4. Steady-state force-[Ca2+]i curves were produced from tetani of various frequencies and tetani produced when force was depressed after fatiguing stimulation. These curves were used to convert [Ca2+]i records into Ca(2+)-derived force. Relaxation of Ca(2+)-derived force was slowed following a time course similar to that of real force. The lag between Ca(2+)-derived and real force during relaxation was not affected by tetanus duration. 5. Tails of elevated [Ca2+]i after tetani were used to analyse the function of the SR Ca2+ pumps. This analysis showed a marked decline in the rate of Ca2+ uptake with prolonged tetani. 6. In conclusion, in Xenopus fibres the slowing of relaxation with increasing tetanus duration can be explained by altered Ca2+ handling due to PA Ca2+ loading and impaired SR Ca2+ uptake. This contrasts to our previous results in mouse fibres and the difference can be explained by a markedly lower rate of SR Ca2+ uptake resulting in higher tetanic [Ca2+]i in Xenopus fibres.
ABBOTT,
The heat production associated with the maintenance of a prolonged contraction and the extra heat produced during large shortening.
1951, Pubmed
ABBOTT,
The heat production associated with the maintenance of a prolonged contraction and the extra heat produced during large shortening.
1951,
Pubmed
Allen,
The effects of caffeine on intracellular calcium, force and the rate of relaxation of mouse skeletal muscle.
1995,
Pubmed
Baylor,
Fura-2 calcium transients in frog skeletal muscle fibres.
1988,
Pubmed
Brum,
Effects of extracellular calcium on calcium movements of excitation-contraction coupling in frog skeletal muscle fibres.
1988,
Pubmed
Cannell,
Effect of tetanus duration on the free calcium during the relaxation of frog skeletal muscle fibres.
1986,
Pubmed
Cleworth,
Changes in sarcomere length during isometric tension development in frog skeletal muscle.
1972,
Pubmed
Fryer,
Actions of caffeine on fast- and slow-twitch muscles of the rat.
1989,
Pubmed
Gillis,
Parvalbumins and muscle relaxation: a computer simulation study.
1982,
Pubmed
Gillis,
Relaxation of vertebrate skeletal muscle. A synthesis of the biochemical and physiological approaches.
1985,
Pubmed
Haiech,
Magnesium and calcium binding to parvalbumins: evidence for differences between parvalbumins and an explanation of their relaxing function.
1979,
Pubmed
Heizmann,
Correlation of parvalbumin concentration with relaxation speed in mammalian muscles.
1982,
Pubmed
Hou,
Effect of temperature on relaxation rate and Ca2+, Mg2+ dissociation rates from parvalbumin of frog muscle fibres.
1992,
Pubmed
Huxley,
Rapid 'give' and the tension 'shoulder' in the relaxation of frog muscle fibres.
1970,
Pubmed
Jackson,
The kinetics of calcium binding to fura-2 and indo-1.
1987,
Pubmed
Klein,
Decline of myoplasmic Ca2+, recovery of calcium release and sarcoplasmic Ca2+ pump properties in frog skeletal muscle.
1991,
Pubmed
Klein,
Simultaneous recording of calcium transients in skeletal muscle using high- and low-affinity calcium indicators.
1988,
Pubmed
Kurebayashi,
Use of fura red as an intracellular calcium indicator in frog skeletal muscle fibers.
1993,
Pubmed
Lattanzio,
The effect of pH on rate constants, ion selectivity and thermodynamic properties of fluorescent calcium and magnesium indicators.
1991,
Pubmed
Lee,
Changes in tetanic and resting [Ca2+]i during fatigue and recovery of single muscle fibres from Xenopus laevis.
1991,
Pubmed
,
Xenbase
Lännergren,
Force and membrane potential during and after fatiguing, continuous high-frequency stimulation of single Xenopus muscle fibres.
1986,
Pubmed
,
Xenbase
Lännergren,
Force relaxation, labile heat and parvalbumin content of skeletal muscle fibres of Xenopus laevis.
1993,
Pubmed
,
Xenbase
Pagala,
Effect of length and caffeine on isometric tetanus relaxation of frog sartorius muscles.
1980,
Pubmed
Peckham,
Labile heat and changes in rate of relaxation of frog muscles.
1986,
Pubmed
Simonides,
Identification and quantification in single muscle fibers of four isoforms of parvalbumin in the iliofibularis muscle of Xenopus laevis.
1989,
Pubmed
,
Xenbase
Stienen,
Relation between force and calcium ion concentration in different fibre types of the iliofibularis muscle of Xenopus laevis.
1987,
Pubmed
,
Xenbase
Stienen,
Uptake and caffeine-induced release of calcium in fast muscle fibers of Xenopus laevis: effects of MgATP and P(i).
1993,
Pubmed
,
Xenbase
Westerblad,
Decreased Ca2-buffering contributes to slowing of relaxation in fatigued Xenopus muscle fibres.
1990,
Pubmed
,
Xenbase
Westerblad,
Slowing of relaxation during fatigue in single mouse muscle fibres.
1991,
Pubmed
Westerblad,
Force and membrane potential during and after fatiguing, intermittent tetanic stimulation of single Xenopus muscle fibres.
1986,
Pubmed
,
Xenbase
Westerblad,
The role of sarcoplasmic reticulum in relaxation of mouse muscle; effects of 2,5-di(tert-butyl)-1,4-benzohydroquinone.
1994,
Pubmed
Westerblad,
Methods for calibration of fluorescent calcium indicators in skeletal muscle fibers.
1994,
Pubmed
Westerblad,
Relaxation, [Ca2+]i and [Mg2+]i during prolonged tetanic stimulation of intact, single fibres from mouse skeletal muscle.
1994,
Pubmed
