Effect of ouabain on myocardial remodeling in rats

The aim of this study was to investigate the effect of ouabain (EO) on myocardial remodeling. Twenty-two adult male Sprague-Dawley rats were randomly divided into two groups: the rats in the EO group (n=12) were intraperitoneally injected with EO daily and those in the control group (n=10) were injected with physiological saline daily. After 8 weeks the rats were sacrificed. The ultrastructural changes in the myocardium were observed. The expression levels of voltage-gated potassium channel 4.2 (K_V4.2) were detected by real-time quantitative reverse transcription-polymerase chain reaction. The effects of EO on the myocardial action potential and transient potassium efflux (I_to) were measured by patch clamping. The systolic blood pressure (SBP) of 10 of the 12 rats in the EO group, designated as the EO-sensitive (OS) rats, began to increase from the fifth week of treatment and was significantly higher compared with that of the control group 6 weeks later (P<0.01). The remaining 2 rats in the EO group that presented no increase in SBP following 8 weeks of treatment (P>0.05) were designated as EO-resistant (OR) rats. Pathological ultrastructural changes were significant in the apical mid-myocardium of the OS rats. No significant differences in K_V4.2 expression were observed among the OS, OR and control rats. The patch clamp results revealed that EO prolongs the action potential duration, reduces I_to and triggers the electrical remodeling of the myocardium. EO induces a blood pressure increase and triggers structural and electrical remodeling.