Impact of Scd4 downregulation on lipolysis in HL-1 cells and primary cardiomyocytes. A: ATGL activity in HL-1 cells with silenced Scd4 expression. B: ATGL activity in primary SCD4-deficient cardiomyocytes treated with stearic acid (C18:0). C: Intracellular calcium concentration in HL-1 cells was measured using the Fluo-4 Direct Calcium Assay Kit according to the manufacturer’s instructions. D: ATGL, E: ABHD5 and G0S2 protein levels in HL-1 cells and results of densitometric analysis. The data are expressed as the mean ± SD. n = 3 independent experiments. (A, C, D, E) ap < 0.05, versus non-targ vehicle; bp < 0.05, versus non-targ 18:0; cp < 0.05, versus siSCD4 vehicle. (B) ap < 0.05, versus WT control; bp < 0.05, versus WT 18:0; cp < 0.05, versus SCD4−/− control. ATGL, adipose triglyceride lipase.