Figure 7. NO synthase uncoupling increases leak at low temperature in WT cardiomyocytes.

(A) NO generation in WT cardiomyocytes measured by detection of DAF-2 fluorescence at 23°C, 25°C, 30°C, 34°C or 37°C. Fluorescence was expressed as relative fluorescence units (F/F₀) by normalization of the DAF-2 signal at each temperature (F) to the fluorescence at 23°C (F₀) (N=4 mice; * p < 0.05 vs. 23°C, one-way ANOVA). (B) Lineal correlation between SR Ca²⁺ leak and NO production in WT cardiomyocytes at all studied temperatures. (C) SR Ca²⁺ leak [at matched SR Ca²⁺ load ≈ 75 μmol/L] in WT cardiomyocytes in the absence (BL) or the presence of 100 μmol/L tetrahydrobiopterin (BH₄) for 2 or 20 minutes (* p < 0.05, Student's t-test). (D) mRNA content of NOS1, NOS2 and NOS3 in WT cardiomyocytes exposed to 23°C, 30°C and 37°C for 30 minutes. (N=4; Student's t-test).