The Effect Of Early Ketamine Exposure On Embryonic Heart Development And Its Molecular Mechanism

Objective: To explore the effect of early ketamine exposure on embryonic heart development in Xenopus laevis.Methods: Xenopus embryos were treated with ketamine from stages 8to 21. Embryonic and cardiac morphology were analyzed using imaging of living embryos and heart tissues, immunofluorescence and whole-mount RNA in situ hybridization(WMISH). Cardiac ultrastructure of embryo was analyzed using transmission electron microscope(TEM). Heart function was measured by heart rate and ventricular shortening fraction(VSF). The mRNA expression levels of several heart development-related genes were determined by Real-time Quantitative PCR(RT-qPCR). The protein expression levels of Xenopus Myosin Light Chain 2(XMLC2) and phospho-histone H3(pH3) were determined by western blot(WB).Results: Ketamine caused concentration-dependent increases in mortality and shortening of body length(P<0.05). At a dose of 0.5 mg/ml,ketamine exposure resulted in cardiac enlargement as the primary manifestation of several malformations: gut defects, a curved axis andshortened body length. Besides, ketamine led to discontinuity and even partial deletion of Z line of cardiac sarcomere ultrastructure. pH3 expression level was increased in embryonic heart(P<0.05). Moreover, the heart rate and ventricular shortening fraction were decreased(P<0.05).XMLC2 mRNA and protein expression levels were down-regulated at four detected stages(P<0.05).Conclusions: Ketamine exposure during early development has concentration-dependent lethality and teratogenic effects on Xenopus embryos, predominantly cardiac enlargement. Cardiac cells undergo increased proliferation. Cardiac sarcomere ultrastructure and heart function are affected. The enlarged heart, abnormal cardiac sarcomere ultrastructure and decreased cardiac contractility may result from the down-regulation of XMLC2 mRNA and protein levels. These findings provide new insight into the potential fetal defects induced by ketamine exposure during early pregnancy.