Abstract
Aequorin, a photoprotein which is regenerated from apoaequorin by incubation with coelenterazine, emits light when it binds Ca 2+. The aim of this study was to determine if apoaequorin could be used in adherent mammalian cells for measuring cytosolic Ca 2+, and imaging Ca 2+, at the single cell level. Chinese hamster ovary (CHO-K1) cells were stably transformed with apoaequorin cDNA and expressed apoaequorin while attached to the culture dishes. Maximal luminescence intensity was obtained when 0.5 × 10 6 cells/ml were grown and incubated with 2.5 μM coelenterazine for 4 hr at 20°C. Ca 2+ mobilizing agents (ionomycin and maitotoxin) induced luminescence in CHO-K1 transformed cells. However, imaging of light emission from single cells proved to be unsuccessful. Ca 2+ could be readily measured in the adherent CHO-K1 cells, but imaging was not possible at the single cell level.
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