Tissue protection by adrenergic blockade in the calcium paradox?

In a graded model of the calcium paradox phenomenon (minimal and total) the presence of the beta-blocker propranolol (5 X 10(-6) M) in the perfusion media (10 min prior to, during and 5 min following calcium-free perfusion) had no effect upon tissue injury. Propranolol pretreatment (three days prior to the experiments) significantly reduced the myocardial enzyme release during calcium repletion in the minimal calcium paradox. The presence of the alpha 1-blocker prazosin (1 X 10(-7) M) in the perfusion media (10 min prior to, during and 5 min following calcium-free perfusion) afforded no protective effects. It is concluded that the release of endogenous catecholamines may not be an important factor contributing to myocardial injury in the calcium paradox, and that consequently beta- or alpha 1-adrenergic blockade has little if any protective properties in this form of myocardial injury.