SPHK1 and myocardial infarction: Indeed, the differences in sphingolipid response observed during cardiac ischaemia between our study and that of Knapp et al. (2009) in which they observed a decrease in S1P levels following MI may be due to the more prolonged ischaemia during MI resulting in degradation of sphingosine kinase 1 (Maceyka et al., 2007) and an inhibition of its activity mediated by ROS leading to decreased levels of S1P and its metabolites (Knapp et al., 2009).