Modes of propagation of Ca(2+)-induced Ca2+ release in bullfrog sympathetic ganglion cells.
How depolarization-induced Ca2+ entry or caffeine activates Ca(2+)-induced Ca2+ release (CICR) in the cytoplasm and nucleoplasm was studied by recording intracellular Ca2+ ([Ca2+]i) with a confocal microscope in cultured bullfrog sympathetic ganglion cells. The amplitude and propagation speed of voltage pulse-induced rises in [Ca2+]i were greater in the submembrane (< 5 microns depth) region than in the core region, and delayed and smaller, but significant, in the nucleus. Ryanodine and dantrolene reduced the rises in [Ca2+]i in both the cytoplasm and nucleus. A rapid application of high K+ solution induced global rises in [Ca2+]i in both the cytoplasm and nucleoplasm, which were decreased by dantrolene. Caffeine produced a slow, small rise in [Ca2+]i which grew into a global, regenerative rise both in the cytoplasm and nucleoplasm with some inward gradient in the cytoplasm. Each of the high [Ca2+]i phases during caffeine-induced [Ca2+]i oscillation began in the submembrane region, while low [Ca2+]i phases started in the core region. These results suggest that CICR activated by Ca2+ entry or caffeine occurs predominantly in the submembrane region causing an inwardly spreading Ca2+ wave or [Ca2+]i oscillations, and that the nuclear envelope can cause CICR in the nucleoplasm, which is delayed due to Ca2+ diffusion barrier at the nuclear pores.
Hua
S Y
SY
Department of Physiology, Saga Medical School, Japan.
Liu
C
C
Lu
F M
FM
Nohmi
M
M
Kuba
K
K
D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D016764:Cell Polarity / Q000187:drug effects; D002478:Cells, Cultured; D003593:Cytoplasm / Q000187:drug effects / Q000378:metabolism; D003620:Dantrolene / Q000494:pharmacology; D005728:Ganglia, Sympathetic / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D007425:Intracellular Membranes / Q000187:drug effects / Q000378:metabolism; D018613:Microscopy, Confocal; D008954:Models, Biological; D011188:Potassium / Q000378:metabolism / Q000494:pharmacology; D011892:Rana catesbeiana; D012433:Ryanodine / Q000494:pharmacology; D019837:Ryanodine Receptor Calcium Release Channel / Q000187:drug effects / Q000378:metabolism
D019837:Ryanodine Receptor Calcium Release Channel; D012433:Ryanodine; D002110:Caffeine; D003620:Dantrolene; D011188:Potassium; D002118:Calcium