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The slow inward Na current observed during sustained depolarization of the Xenopus oocyte membrane is due to a complex mechanism described as the induction of the channels. The present work investigates the role of protein phosphorylation in Na channel function. Injection of alkaline phosphatase in the oocytes decreased inward current. Therefore, the(More)
Inhibition of calmodulin (CaM) sensitizes Ca2+ release mediated by D-myo-inositol (1,4,5)-trisphosphate (InsP3) in Xenoplus oocytes, which results in spontaneous Ca2+ -dependent Cl- current oscillations or in a shift of the concentration threshold for lysophosphatidic acid (LPA) by a tenfold factor. The oscillatory currents appear at a low initial Ca2+(More)
Activation of the phosphoinositide transduction pathway induces capacitative Ca2+ entry in Xenopus oocytes. This can also be evoked by intracellular injection of Ins(1,4.5)P3, external application of thapsigargin and/or incubation in a Ca2+-free medium. Readmission of Ca2+ to voltage-clamped, thapsigargin-treated Xenopus oocytes triggers Ca2+-dependent Cl-(More)
Caffeine increases the amplitude of the Cl- currents evoked by capacitative Ca2+ entry (CCE) on thapsigargin-treated Xenopus oocytes. The caffeine-induced potentiation of the CCE process appears to rest on two distinct and additive components. The first component involves the cAMP second messenger system since it can be mimicked by either IBMX perfusion or(More)
Xenopus oocytes injected with rat cerebellar mRNA expressed functional voltage-dependent Ca channels detected as an inward Ba current (IBa). The pharmacological resistance to dihydropyridines and omega-conotoxin together with the blockade obtained with Agelenopsis aperta venom suggest that these channels could be somehow assimilated to P-type Ca channels.(More)
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(More)
The effect of Ca2+ on inositol (1,4,5)-trisphosphate 3-kinase (3-kinase) activity was measured on Xenopus oocyte cytosolic extracts. The Ca2+-evoked elevation in 3-kinase activity appeared to be mediated by calmodulin (CaM) and the calmodulin-dependent protein kinase II (CaMKII). The results observed in vitro were totally retrieved in intact oocytes and(More)
The expression in Xenopus oocytes of the human voltage-dependent Ca2+ channel (VDCC) beta 2 subunit subtype (h beta 2) enhances the endogenous Ca2+ channel activity. By using the native Ca(2+)-dependent chloride conductance to monitor fast intracellular Ca2+ variations, we point out that the beta-enhanced Ca2+ entry (T1 component) is currently associated(More)
Endogenous calcium channels of Xenopus oocyte membrane do not fit with pharmacological classification of calcium channels. The present study demonstrates that the saccharidic derivate, OC8-MAGlu-MAGlu, has potent inhibitory effect on this channel activity.
Rat cerebellar RNA injected into Xenopus oocytes leads to the expression of putative P-type voltage-dependent Ca2+ channels (VDCCs). The monitoring of intracellular Ca2+ variations by recording the Ca2+ dependent chloride current in voltage clamped oocytes indicates that activation of these Ca2+ channels by depolarization gives rise to two distinct(More)