Effect of SERCA pump inhibition by thapsigargin on 20 mM caffeine-induced [Ca²⁺]_i responses.

<p>(A) [Ca²⁺]_i responses of 12 different cells that were exposed to thapsigargin for 5 seconds, 30 seconds before the application of caffeine, were smaller in amplitude and slower and (B) with a larger rise time. The mathematical model fitted this relationship but only after switching from KonD model to SK model (blue lines). (C) Time course of the [Ca²⁺]_i response to 20 mM caffeine from a cell that had been previously exposed to thapsigargin together with fitting by modified SK model (blue line) and the resulting reduction in the [Ca²⁺]_SR from this model (green line). Notice there was no recovery of the [Ca²⁺]_FSR as expected for inhibited SERCA pumps.