Expression of calcium channels in Xenopus oocyte injected with crab skeletal muscle fibre mRNA.
Using the whole cell voltage-clamp technique and a C1 free and Na free Ba methane sulfonate solution, stage V and VI Xenopus oocytes demonstrated a Ba current (endogenous component) with a peak amplitude average of 6 nA (6 +/- 2 nA). When oocytes were injected with crustacean skeletal muscle mRNA, an additional component of IBa could be detected (exogenous IBa). The latter current could be distinguished from the native one by several electrophysiological means: a peak amplitude average of 90 nA (90 +/- 4 nA), activation potential threshold, steady state inactivation properties and sensitivity to Ca blockers. As shown by Jdaïâa and Guilbault in crustacean skeletal muscle fibres, exogenous IBa could be divided into two components: a "fast component" and a "slow component" probably passing through two types of Ca channels (fast and slow) since the peak Ba current voltage relationship was biphasic and the fast component of exogenous IBa was less sensitive than the slow to nifedipine. The features of the newly synthesized channels incorporated in the Xenopus oocyte membrane suggest that they may be associated with fast and slow channels, previously described in many preparations, particularly in crustacean skeletal muscle fibres.
Fournier
F
F
Laboratoire de Physiologie Cellulaire, Université des Sciences et Techniques de Lille, France.
Jdaïâa
H
H
Lory
P
P
Brûlé
G
G
Curgy
J J
JJ
Guilbault
P
P
D000818:Animals; D003386:Brachyura / Q000235:genetics / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism*; D008564:Membrane Potentials / Q000502:physiology; D008565:Membrane Proteins / Q000096:biosynthesis* / Q000235:genetics; D008845:Microinjections; D009865:Oocytes / Q000378:metabolism; D011061:Poly A; D014176:Protein Biosynthesis; D012333:RNA, Messenger; D014982:Xenopus laevis / Q000235:genetics
D015220:Calcium Channels; D008565:Membrane Proteins; D012333:RNA, Messenger; D011061:Poly A