Extracellular Ca(2+)-dependent and independent calcium transient in fetal myotubes.
Spatio-temporal changes in the intracellular calcium concentration [Ca2+]i of dissociated mice myotubes from 14-day and 18-day-old fetuses were studied using digital imaging analysis of the Ca2+ indicator fura-2. Myotubes from 18-day-old fetuses displayed a transient [Ca2+]i increase upon electrical stimulation either in nominally calcium-free external solution or in Krebs solution containing 100 microM lanthanum. Thus, at this developmental stage, membrane depolarization appears to increase [Ca2+]i by stimulating Ca2+ release from the sarcoplasmic reticulum independently of extracellular Ca2+ influx. Similarly, myotubes from 14-day-old fetuses also showed a calcium transient upon electrical stimulation in Krebs solution. However, in 46% of these myotubes the calcium transient was abolished when Ca2+ entry through calcium channels was suppressed.
Laboratoire de Neurobiologie Cellulaire et Moléculaire, CNRS, Gif-sur-Yvette, France.
C
C
Strube
M
M
Beurg
D
D
Georgescauld
R
R
Bournaud
T
T
Shimahara
D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D015220:Calcium Channels / Q000378:metabolism*; D004558:Electric Stimulation; D005260:Female; D016257:Fura-2; D007091:Image Processing, Computer-Assisted; D066298:In Vitro Techniques; D007366:Intercostal Muscles / Q000196:embryology / Q000378:metabolism* / Q000648:ultrastructure; D007811:Lanthanum / Q000494:pharmacology; D051379:Mice; D008870:Microtubules / Q000378:metabolism* / Q000502:physiology; D011247:Pregnancy
D015220:Calcium Channels; D007811:Lanthanum; D002118:Calcium; D016257:Fura-2