Intermolecular Failure of L-type Ca2+ Channel and Ryanodine Receptor Signaling in Hypertrophy
Figure 2
Triggering a Ca2+ Spark by Activating a Single LCC
(A) Representative loose-patch confocal images (left) and their time profiles (right) show that a 70-mV depolarization from resting potential evoked RyR Ca2+ sparks (high-amplitude, rapid-takeoff events) and LCC Ca2+ sparklets (flat, slow events) in a stochastic manner. Images were selected from the control (top, showing two sparks that were triggered), CHT (middle, showing the first sparklet, with a 21-ms time to peak, that failed to trigger a spark), and DHT (bottom, showing two sparklets without triggering sparks) groups.
(B) and (C) The amplitude (B) and the time to peak (C) of Ca2+ sparks did not differ among groups. Each datum was an average of more than 120 events from six or more animals. The bars represent the following groups: open bar, control; gray bar, CHT; and solid bar, DHT.
(D) and (E) The “hit index” (D) represents the percentage of Ca2+ sparks that were apparently triggered by the first Ca2+ sparklets, whereas the “miss index” (E) denotes the percentage of depolarization pulses that did not trigger any Ca2+ sparks. The percentages were first calculated on a single-cell basis, and then averaged among more than 50 cells from six or more animals. The bars represent the following groups: open bar, control; gray bar, CHT; and solid bar, DHT.