The possible mechanism of protection induced by dexamethasone against sudden death due to coronary ligation in conscious rats.

Rat isolated peritoneal cells (10(7) cells ml-1) incubated in the presence of dexamethasone (3 X 10(-9) M, for 90 min) were shown to release some factor(s), having a mol. wt. of 15 k, as determined by size exclusion chromatography, which inhibited phospholipase A2 activity and offered significant protection against sudden death due to post-infarction arrhythmias in conscious rats pretreated with actinomycin D (0.5 mg kg-1 i.v. 4 h before coronary ligation). This observation suggests that the cardioprotective effect of glucocorticoids in acute myocardial infarction may result from the de novo synthesis of macrocortin, an antiphospholipase protein.