Figure 5.

Ca²⁺ Transients and Ca²⁺ Handling Proteins After 7 Days of Continuous Iso Infusion

(A–D) Ca²⁺ transients. (A) Representative Indo-1 Ca²⁺ recordings from cardiac myocytes from C1C2 and Con mice after 7 days of Iso infusion. (B) Basal Ca²⁺ release (systolic-diastolic Ca²⁺) show increased Ca²⁺ release in C1C2 cardiac myocytes (p = 0.02). (C) Time to peak Ca²⁺ transient was reduced in C1C2 cardiac myocytes (p = 0.002). (D) Time to Ca²⁺ decline (Tau) was reduced in cardiac myocytes from C1C2 mice (p = 0.04). (E) LV SERCA2a content was 2.6-fold greater in C1C2 than in Con mice after 7 days of Iso infusion (p = 0.002; immunoblot below bar graph), although before Iso infusion, the fold difference (C1C2 vs. Con) was not significant (p = 0.29). (F) Cardiac-directed C1C2 expression was associated with an 11.5-fold increase in LV P-Rex2 mRNA before (p = 0.001) and 7.5-fold after 7 days of Iso infusion (p = 0.002) vs. Con. (G) No group differences in expression of PKA, PLB, S100A1, or vinculin were seen. Phosphorylation of PKA, PLB, and TnI also showed no group differences. Bars = mean values; SE = error bars; number in bars = numbers of cells (B to D) or mice (E, F); numbers above bars = p values from Student t-test (unpaired, 2-tailed). Abbreviations as in Figures 1, 2, 3, 4, and 5.