AIMTo study the varies and effects of ischemic preconditioning of myocardium on every part of adrenergic receptor-adenyl cyclase system in rats in vivo.

METHODSSD rats were randomly divided into three groups: CON group (n = 6), IP group (n = 12) and I/R group (n = 12). Surgical procedure included intermittent left coronary artery occlusion and reperfusion. After the procedure, the hearts were extracted. We analyzed the infarct size by TTC staining, measured serum myocardial enzymes, studied the beta-AR Bmax and KD by radioligand binding assay of receptors (RAB), and checked the activity of AC and the content of cAMP by radioimmunoassay (RIA).

RESULTSInfarct area were much smaller in IP group than in I/R group (P < 0.05). CK, CK-MB, LDH were significantly higher in I/R group (P < 0.01). The Bmax of beta-AR in IP group were much higher than in I/R group (P < 0.01). No difference of KD could be seen between IP and I/R group. In IP group, the activity of AC and the content of cAMP were higher than I/R group (P < 0.05).

CONCLUSIONIschemic preconditioning can protect the heart from necrosis and reduce endo-enzyme leakage. Ischemic preconditioning can increase the density of beta-AR, the activity of AC and the content of cAMP, which shows that the system of adrenergic receptor-adenyl cyclase system probably takes part in the protection of IP.