[The role of mu- and delta-opiate receptors in resistance of the myocardium to free radical damage].

I.v. administration of the delta-opioid (OR) receptors' agonists DSLET or DTLET prevented creatine kinase leakage from the rat isolated heart in oxidative stress damage and abolished an increase in myocardial levels of conjugated diens and malondialdehyde. The agonists also prevented a stress-induced augmentation of the superoxide dismutase (SOD) activity. All protective effects of delta-receptor stimulation was completely abolished by the delta OR antagonist ICI 174,864. The data obtained suggest that the cardioprotective effect of the delta OR stimulation in vivo is not mediated via direct cardiac delta OR activation but, probably, rather via some unknown indirect circulating humoral factor(s).