Blink nadir measurements of sarcoplasmic reticulum are consistent with strong local Ca²⁺ depletion.

ABSTRACT: Ca²⁺ blinks measure the exit of Ca²⁺ from the junctional sarcoplasmic reticulum (JSR) in a cardiac myocyte during a Ca²⁺ spark. Here, the relationship between experimental blink fluorescence measurements and the [Ca²⁺] in the JSR is explored using long 3D simulations of diastolic Ca²⁺ release. For a fast intra-SR Ca²⁺-activated fluorophore such as Fluo-5N, we show that a simple mathematical formula relates the two for an ideal blink (i.e., when fluorescence signals come only from the JSR). The formula shows that normalized JSR [Ca²⁺] is much lower than the normalized fluorescence and that JSR Ca²⁺ depletes ∼40-50% more than previously inferred from blink fluorescence measurements. In addition, we show t

SUBMITTER: Gillespie D 

PROVIDER: S-EPMC11788478 | biostudies-literature | 2025 Jan

REPOSITORIES: biostudies-literature