FIGURE 4.

RyR inhibition reduces Ca²⁺ leakage from the store and facilitates store refilling in Jurkat YC4.2er cells. A, representative traces showing changes in [Ca²⁺]_ER in control cells preincubated with vehicle alone (Ctl; black trace), 400 μm Ry (blue trace), or 30 μm DS (red trace). Prior to taking measurements, the CPA was applied for 10 min and then washed out for 10 min in Ca²⁺-free bath solution. Nominally Ca²⁺-free (0 Ca) and 2 mm Ca²⁺-containing (2 Ca) extracellular solutions were applied as indicated. The raw F₅₃₅/F₄₈₀ values, which are proportional to [Ca²⁺]_ER, were normalized so that F₅₃₅/F₄₈₀ values determined just before the first application of 2 mm Ca²⁺-containing solution and 1.5 min after the second application of 2 mm Ca²⁺-containing solution were taken as 0 and 100%, respectively. Inset, expansion of the boxed area. Traces were aligned at the time of Ca²⁺-free bath solution application. The time constant (τ) of the F₅₃₅/F₄₈₀ decay was determined by fitting the initial 60-s segment of normalized F₅₃₅/F₄₈₀ traces recorded following application of Ca²⁺-free bath solution with a single exponential function (smooth lines in the inset). B, average values of τ obtained in control cells preincubated with vehicle alone (Ctl; black bar; n = 9), Ry (blue bar; n = 5), or DS (red bar; n = 4). *, differences between means are significant (p < 0.05). Error bars, S.E.