Dependence of Ca2+ and K+ current development on RNA and protein synthesis in muscle-lineage cells of the ascidian Boltenia villosa.
The early development of excitability of muscle-lineage cells of the ascidian Boltenia villosa is characterized by the appearance, just after gastrulation, of a Ca2+ current and a delayed outward K+ current, while an inwardly rectifying K+ current, present since fertilization, disappears. The muscle-lineage cells are the first cells in which we detect tissue-specific electrical properties after gastrulation. Here, we show that the development of electrical properties in these cells involves RNA and protein synthesis. If transcription or translation is blocked, the Ca2+ and outward K+ currents fail to appear, whereas the inward K+ current disappears normally. For the Ca2+ current, the sensitive period for transcription extends until just before gastrulation, while the sensitive period for translation extends until after gastrulation. The oocyte has a Ca2+ current present at about 5-10% the density of that in the muscle-lineage cells; this current disappears by gastrulation. A comparison of the oocyte and muscle Ca2+ currents indicates that they are similar in voltage dependence and inactivation mechanism. A small difference in permeability sequence can be attributed to different surface charge properties at the two stages of development.
Simoncini
L
L
Department of Zoology, University of Washington, Seattle 98195.
Moody
W J
WJ
D000818:Animals; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D003609:Dactinomycin / Q000494:pharmacology; D004594:Electrophysiology / Q000379:methods; D004625:Embryo, Nonmammalian / Q000502:physiology; D005775:Gastrula / Q000502:physiology; D008564:Membrane Potentials; D009130:Muscle, Smooth / Q000502:physiology*; D009865:Oocytes / Q000502:physiology; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D014176:Protein Biosynthesis; D011506:Proteins / Q000235:genetics; D012313:RNA / Q000096:biosynthesis* / Q000235:genetics; D014561:Urochordata / Q000196:embryology / Q000502:physiology*
D015220:Calcium Channels; D015221:Potassium Channels; D011506:Proteins; D003609:Dactinomycin; D012313:RNA