Cardiac electrical and contractile disorders promoted by anabolic steroid overdose are associated with late autonomic imbalance and impaired Ca2+ handling

Abstract

AimInvestigate cardiac electrical and mechanical dysfunctions elicited by chronic anabolic steroid (AS) overdose. MethodsMale Wistar rats were treated with nandrolone decanoate (DECA) or vehicle (CTL) for 8 weeks. Electrocardiography and heart rate variability were assessed at weeks 2, 4, and 8. Cardiac reactivity to isoproterenol was investigated in isolated rat hearts. Action potential duration (APD) was measured from left ventricular (LV) muscle strips. L-type Ca2+ current (ICaL), and transient outward potassium current (Ito) were recorded by whole-cell patch-clamp in LV cardiomyocytes. Sarcoplasmic reticulum (SR) Ca2+ mobilization and Ca2+-induced contractile response sensitivity were evaluated in skinned cardiac fibers. Muscarinic type 2 receptor (M2R), β1-adrenergic receptor (β1AR), sarcoplasmic Ca2+ ATPase (SERCA-2a), type 2 ryanodine receptor (RyR2), L-type Ca2+ channel (CACNA1), Kv4.2 (KCND2), and Kv4.3 (KCND3) mRNA expression levels were measured by quantitative RT-PCR. ResultsCompared with CTL group, DECA group exhibited decreased high frequency band power density (HF) and increased low frequency power density (LF), Cardiac M2R mRNA level was decreased. QTc interval at 2nd, 4th, and 8th week as well as APD30 and APD90 were increased by DECA. Ito density was decreased, while ICaL density was increased by DECA. SR Ca2+ loading and release were decreased by DECA, while contractile sensitivity to Ca2+ was increased versus CTL group. ConclusionDECA overdose induced cardiac rhythmic and mechanical abnormalities that can be associated with autonomic imbalance, up-regulated ICaL and down-regulated Ito, abnormal SR Ca2+ mobilization, and increased contractile sensitivity to Ca2+.