Results from analysis of miR-208b-overexpressing HL-1 atrial myocytes and from myocytes isolated from CAF patients showed that aberrant miR-208b levels reduced the expression and function of L-type Ca<sup>2+</sup> channel subunits (CACNA1C and CACNB2) as well as the sarcoplasmic reticulum-Ca<sup>2+</sup> pump SERCA2.
Luciferase reporter assays demonstrated that miR-21 produced a concentration-dependent decrease in the luciferase activity in Chinese Hamster Ovary cells transfected with CACNA1C and CACNB2 3' untranslated region regions. miR-21 transfection in HL-1 cells produced changes in I(Ca,L) properties qualitatively similar to those produced by CAF (ie, a marked reduction of I(Ca,L) density and shift of the inactivation curves to more depolarized potentials).