Catecholaminergic polymorphic ventricular tachycardia (CPVT) is associated with mutations in the cardiac ryanodine receptor (RyR2). These result in stress-induced ventricular arrhythmic episodes, with clinical symptoms and prognosis reported more severe in male than female patients. Murine homozygotic RyR2-P2328S (RyR2 S/S) hearts replicate the proarrhythmic CPVT phenotype of abnormal sarcoplasmic reticular Ca 2+ leak and disrupted Ca 2+ homeostasis. In addition, RyR2 S/S hearts show decreased myocardial action potential conduction velocities (CV), all features implicated in arrhythmic trigger and substrate. The present studies explored for independent and interacting effects of RyR2 S/S genotype and sex on expression levels of molecular determinants of Ca 2+ homeostasis (CASQ2, FKBP12, SERCA2a, NCX1, and Ca V 1.2) and CV (Na V 1.5, Connexin (Cx)-43, phosphorylated-Cx43, and TGF-β1) in mice. Expression levels of Ca 2+ homeostasis proteins were not altered, hence implicating abnormal RyR2 function alone in disrupted cytosolic Ca 2+ homeostasis. Furthermore, altered Na V 1.5, phosphorylated Cx43, and TGF-β1 expression were not implicated in the development of slowed CV. By contrast, decreased Cx43 expression correlated with slowed CV, in female, but not male, RyR2 S/S mice. The CV changes may reflect acute actions of the increased cytosolic Ca 2+ on Na V 1.5 and Cx43 function.