Calcium Homeostasis and Cone Signaling Are Regulated by Interactions between Calcium Stores and Plasma Membrane Ion Channels
Figure 3
Tonic Mn2+ influx into ‘resting’ cones is modulated by calcium stores.
(A) Cone depolarized with 60 mM KCl. 100 µM Mn2+ quenches Fura-2 fluorescence evoked by 340 and 380 nm excitation. Addition of 10 µM ionomycin evokes little additional quenching, indicating that most of the indicator dye is confined to the cytosol. (B) Fura-2 fluorescence evoked by 360 nm excitation. At rest, the dye bleaches at a rate that reflects loading and excitation strength (arrowhead). Addition of 50 µM Mn2+ causes quenching of the dye; (C) The rate of quenching is insensitive to verapamil (50 µM) and antagonized by Gd3+ (10 µM). (C) CPA (5 µM), increased the slope of Fura-2 quenching in a subset of cones. (D) Summary of the data for Mn2+ quenching experiments.