Activation of Adenylate Cyclase System in the Preconditioned Rat Heart

OKRUHLICOVÁ, T. RAVINGEROVÁ, D. PANCZA, N. TRIBULOVÁ, J. STYK, R. ŠTETKA

Received April 16, 1999
Accepted September 24, 1999

Summary
Ischemic preconditioning (IP) protects the heart against subsequent prolonged ischemia. Whether the
beta-adrenoceptor/adenylate cyclase pathway contributes to this cardioprotection is not yet fully known. Using enzyme catalytic cytochemistry we studied the adenylate cyclase activity and its distribution in the preconditioned rat heart.Adenolyse cyclase activity was examined in Langendorff perfused rat hearts subjected to the following conditions: control perfusion; 30 min regional ischemia; 5 min occlusion and 10 min reperfusion (IP); IP followed by ischemia. Ischemia-induced arrhythmias and the effect of ischemic preconditioning on the incidence of arrhythmias were analyzed. At the end of experiment the heart was shortly prefixed with glutaraldehyde. Tissue samples from the left ventricle were incubated in a medium containing the specific substrate AMP-PNP for adenylate cyclase and thenroutinely processed for electron microscopy. Adenylate cyclase activity was cytochemically demonstrated in the  sarcolemma and the junctional sarcoplasmic reticulum (JSR) in control hearts, while it was absent after test ischemia. The highest activity of the precipitate was observed after ischemic preconditioning. In the preconditioned heartsfollowed by test ischemia, adenylate cyclase activity in the precipitate was preserved in sarcolemma and even more inJSR. Protective effect of ischemic preconditioning was manifested by the suppression of severe arrhythmias. These results indicate the involvement of the adenylate cyclase system in mechanisms underlying ischemic preconditioning.

Key words
Preconditioning · Adenylate cyclase · Cytochemistry · Rat · Heart
 

Reprint requests
L. Okruhlicová, Institute for HeartResearch, Slovak Academy of Sciences, Dúbravská cesta 9, 842 33 Bratislava, Slovak Republik, e-mail: usrdokru@savba.sk