A review on Late phase ischemic preconditioning.

Ischemic preconditioning consists of brief episode of sub lethal ischemia followed by reperfusion. It is a biphasic phenomenon, which starts within minutes and get wanes off gradually within 2 to 3 hours and also called as classical preconditioning and the other phase which appear after 12-24 hours called as late phase of ischemic preconditioning (or delayed phase) which lasts up to 3 to 4 days also called as second widow of protection. Unlike the early phase of ischemic preconditioning, the late phase of ischemic preconditioning protects not only against the myocardial infarction but also include protection against myocardial stunning. Both these phases, early and delayed are responsible for the protection against myocardial infarction and myocardial stunning. Late phase of ischemic preconditioning involves certain mechanisms that includes first one as those species which are generated during the starting ischemic insult and responsible for the activation of late preconditioning triggers. Second mechanism includes those which are activated after 24- 72 hours of the ischemic insult and responsible for the activation of mediators of late preconditioning. The third one is activated by the action of triggers to show the actions of mediators. All these mechanism are in sequences, former is upstream signal for the next one and they were activated only after preconditioning stimulus. This phenomenon of ischemic preconditioning shows its benificial effect via involvement of certian triggers and meditors like COX-2, NO, Aldose reductase, etc.