Regenerative release of calcium from functionally discrete subcellular stores by inositol trisphosphate.
Fluorescence imaging was used to determine the spatial and temporal patterns of subcellular calcium (Ca2+) liberation induced in Xenopus oocytes by photorelease of inositol 1,4,5-trisphosphate (InsP3) from a caged precursor. Increasing levels of InsP3 evoked Ca2+ release that began in a graded manner but, at varying threshold levels of InsP3, localized sites then showed transient and asynchronous 'puffs' of Ca2+ release. With higher levels of InsP3, Ca2+ from adjacent sites formed a focus for initiation of a propagating Ca2+ wave. The results show that InsP3-sensitive Ca2+ stores are arranged as distinct and functionally independent units, and that Ca2+ is released in both graded and regenerative fashions.
Parker
I
I
Department of Psychobiology, University of California, Irvine 92717.
Yao
Y
Y
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D005260:Female; D015544:Inositol 1,4,5-Trisphosphate / Q000494:pharmacology*; D007700:Kinetics; D009865:Oocytes / Q000187:drug effects / Q000502:physiology*; D013997:Time Factors; D014982:Xenopus laevis
D015544:Inositol 1,4,5-Trisphosphate; D002118:Calcium