Effect of IK1 agonist zacopride on L-thyroxine-inducedventricular remodeling in rats / 中国药理学通报

ABSTRACT

Aim To examine the effect of zacopride,a specific inward rectifier potassium channel(IK1)agonist,on L-thyroxine(T4)-induced ventricular remodeling and the underlying mechanism.Methods SD rats were randomly divided as control,L-thyroxine(L-thy,1 mg·kg-1·d-1,ig,10 d)model,L-thy +zacopride(5,15,50 μg·kg-1,respectively,ip),L-thy+zacopride(15 μg·kg-1)+chloroquine(7.5 μg·kg-1,ip)and L-thy+captopril(100 mg·kg-1·d-1,drinking water)groups.Echocardiography and cardiac hypertrophic indexes were measured to confirm the establishment of the ventricular remodeling model.The changes of IK1 and L-calcium current(ICa-L)were detected by whole cell patch clamp technique.The confocal microscopy and fluorescent indicator Fluo-4 were applied to examine the intracellular Ca2+ concentration([Ca2+]i)of isolated adult rat ventricular myocytes.Results L-thyroxine induced left ventricular hypertrophy with increased ratio of heart weight(HW)to body weight(HW·BW-1),ratio of left ventrical weight(LVW)to body weight(LVW·BW-1),left ventricular dimension in diastole(LVIDd),left ventricular dimension in systole(LVIDs),interventricular septum thickness(IVS)and decreased ejection fraction(EF),fractional shortening(FS)(P<0.01).Patch clamp data suggested IK1 was downregulated,while ICa-L was upregulated(P<0.01).In isolated adult cardiomyocytes,L-thyroxine increased the cell area and [Ca2+]i(P<0.01).Zacopride treatment obviously alleviated cardiac remodeling,improved cardiac function,reversed the changes of IK1 and ICa-L,and significantly attenuated intracellular calcium overload(P<0.01).The optimum dose of zacopride in vivo was 15 μg·kg-1 at which the effect was compared favourably with captopril,a classical anti-remodeling agent.Low-dose IK1 atagonist chloroquine could reverse the effect of zacopride(P<0.01).Conclusion Via activating IK1,zacopride could significantly decrease Ca2+ influx and intracellular calcium overload thereby inhibiting L-thyroxine-induced cardiac ventricular remodeling.