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.
XB-ART-17889
Biophys J 1996 Aug 01;712:908-17.
Show Gene links Show Anatomy links

Intracellular calibration of the calcium indicator indo-1 in isolated fibers of Xenopus muscle.

Westerblad H , Allen DG .


???displayArticle.abstract???
Estimates of the free myoplasmic [Ca2+] ([Ca2+]i) with fluorescent dyes are complicated by the fact that some properties of these dyes are altered in the intracellular environment. In the present study indo-1 was used to measure [Ca2+]i in isolated muscle fibers from Xenopus frogs. Fluorescent ratio signals obtained from indo-1 were converted into [Ca2+]i by means of an intracellular calibration method, which involved microinjection of 0.5 M EGTA and 1 M CaCl2 to get the ratio at very low (Rmin) and high (Rmax) [Ca2+], respectively; ratios at intermediate [Ca2+] were obtained by injection of solutions with different EGTA/Ca(2+)-EGTA proportions. This calibration gave an intracellular Ca2+ dissociation constant of indo-1 of 311 nM and a [Ca2+]i at rest of 52 +/- 4 nM (mean +/- SE; n = 15). Indo-1 records during twitches were compared with records obtained with the much faster indicator mag-indo-1. This analysis suggests a Ca2+ dissociation rate of indo-1 of 52 s-1 (22 degrees C). This makes indo-1 less suitable for measurements of [Ca2+]i during twitches, whereas it is fast enough to follow most aspects of [Ca2+]i during tetani, including the relaxation phase.

???displayArticle.pubmedLink??? 8842230
???displayArticle.pmcLink??? PMC1233548
???displayArticle.link??? Biophys J


Species referenced: Xenopus laevis
Genes referenced: ido1 mag

References [+] :
Allen, Intracellular calcium and tension during fatigue in isolated single muscle fibres from Xenopus laevis. 1989, Pubmed, Xenbase