Voltage dependence of the [Ca2+](i) oscillations system, in the Mg2+ -stimulated oocyte of the prawn Palaemon serratus.
By voltage-clamp technique and simultaneous [Ca2+](i)measurements, we studied the modifications, induced by changes in membrane voltage, in the pattern of the [Ca2+](i)oscillation period, displayed by the Mg2+-stimulated oocyte of the prawn Palaemon serratus. When the Mg2+-stimulated oocytes were voltage clamped at 0mV, they developed a [Ca2+](i)signal with a more pronounced oscillatory pattern than that obtained on unclamped oocytes. Indeed, they displayed a first peak followed by a series of sharp [Ca2+](i)transients and a prominent [Ca2+](i)oscillatory plateau. By contrast, oocytes voltage clamped at - 60mV showed a first peak followed by a stable high [Ca2+](i)level forming a long continuous plateau devoid of oscillations. By using caged InsP3, we established that the ER InsP3 receptor is not voltage sensitive. Paradoxically, we showed the voltage sensitivity of the Mg2+ receptor-signal transduction system which is more reactive to Mg2+ ions at -60mV than at 0mV. Using different calmodulin inhibitors of the PM CA pump such as trifluoperazin (100microM), W-7 (50microM) and calmidazolium (50microM), we suppressed the [Ca2+](i)oscillatory pattern in oocytes voltage clamped at 0mV. From these results we propose that this special voltage-dependent oscillatory system could be regulated by a significant involvement of the electrogenic PM CA pump.
Goudeau
H
H
Observatorie Océanographique et de Biologie marine de Roscoff, UPR C.N.R.S. 9042 and Université et Marie Curie, Roscoff, France. hgoudeau@sb-roscoff.fr
Goudeau
M
M
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D018492:Dopamine Antagonists / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005456:Fluorescent Dyes; D007093:Imidazoles / Q000494:pharmacology; D053496:Inositol 1,4,5-Trisphosphate Receptors; D008274:Magnesium / Q000494:pharmacology*; D008297:Male; D008564:Membrane Potentials / Q000502:physiology; D008845:Microinjections; D009865:Oocytes / Q000187:drug effects* / Q000502:physiology; D033541:Palaemonidae; D018408:Patch-Clamp Techniques; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D013449:Sulfonamides / Q000494:pharmacology; D014268:Trifluoperazine / Q000494:pharmacology
D015220:Calcium Channels; D018492:Dopamine Antagonists; D004791:Enzyme Inhibitors; D005456:Fluorescent Dyes; D007093:Imidazoles; D053496:Inositol 1,4,5-Trisphosphate Receptors; D018160:Receptors, Cytoplasmic and Nuclear; D013449:Sulfonamides; D014268:Trifluoperazine; C031938:calmidazolium; C017967:W 7; D008274:Magnesium; D002118:Calcium