We studied the effects of the aminosteroid U-74389G (21-[4-(2, 6-di-1-pyrrolidinyl-4-pyrimidinyl)-1-piperazinyl]-pregna-1,4,9(11)- triene-3,20-dione(2)-2-butenenedionate), a putative inhibitor of lipid peroxidation, which protects the rat myocardium after ischemia and reperfusion. Pentobarbital-anesthetized (50 mg/kg) rats were subjected to 60 min of occlusion of the left main coronary artery followed by 60 min of reperfusion. Myocardial ischemia/reperfusion produced a large cardiac necrosis (81 +/- % of the area at risk and 65 +/- % of the total left ventricle), polymorphonuclear infiltration in the jeopardized tissue (myeloperoxidase activity = +/- U X 10(-3)/g tissue in the area at risk and +/- U X 10(-3)/g tissue in the necrotic area), hydroxyl radical (OH.) formation ( +/- nmol/ml), increased plasma malonylaldehyde ( +/- nmol/ml) and lactate dehydrogenase (431 +/- 30 mIU/ml) and caused a decrease in the survival rate. Treatment with U-74389G (15 and 30 mg/kg .) at the onset of reperfusion caused a reduction of necrotic area expressed as a percentage of either the area at risk (76 +/-% with 15 mg/kg and 69 +/- % with 30 mg/kg; P < .05) or the total left ventricle (53 +/- % with 15 mg/kg and 46 +/- % with 30 mg/kg; P < .05). Treatment U-74389G reduced the myeloperoxidase activity, evaluated as an index of neutrophil infiltration, both in the area at risk ( +/- and +/- U X 10(-3)/g tissue with the doses of 15 and 30 mg/kg, respectively; P < .05) and in the necrotic area ( +/- and +/- U X 10(-3)/g tissue with 15 and 30 mg/kg, respectively; P < .05); decreased OH. formation (measured indirectly by the administration of the trapping agent salicylic acid); and analyzing the hydroxylation product 2,5-dihydroxybenzoic acid during reperfusion ( +/- and +/- nmol/ml with the doses of 15 and 30 mg/kg, respectively; P < .005). Treatment inhibited lipid peroxidation by blunting plasma malonylaldehyde ( +/- and +/- with the doses of 15 and 30 mg/kg, respectively; P < .001), prevented cellular disruption by reducing the increase of plasma lactate dehydrogenase ( +/- 28 and +/- 16 mIU/ml with the doses of 15 and 30 mg/kg, respectively; P < .001). Finally, U-74389G enhanced the survival rate evaluated at the end of the experiment (from 40 to 87%). These outcomes suggest that the drug may have potential for cardioprotective use in acute myocardial infarction.
AB - Objective: To determine if a new class of agents, the 21-aminosteroids, which are reportedly potent inhibitors of iron-dependent lipid peroxidation, could protect rats from bleomycin-induced pulmonary fibrosis. Subjects: Fifty-five adult male Sprague-Dawley rats. Design: Prospective, randomized, blinded, controlled trial. Interventions: The rats were subjected to intratracheal bleomycin (or saline vehicle), and were then treated with the 21-aminosteroid, U74389F (20 mg/kg/day), or vehicle, for the next 7 days. Measurements and Main Results: At 21 days after bleomycin administration, pulmonary fibrosis was assessed histologically as percent of lung fields with evidence of fibrosis. Pulmonary fibrosis was assessed biochemically by measuring pulmonary elastin and hydroxyproline content. To determine if a protective effect of U74389F was linked to the 21-aminosteroid's ability to suppress lipid peroxidation, two products of lipid peroxidation were assayed in the lungs at 7 and 14 days after bleomycin exposure. By histologic assessment, the 21-aminosteroid-treated, bleomycin-exposed animals were found to have significantly decreased the extent of pulmonary fibrosis when compared with the bleomycin control group (mean ± [SD] % [n = 9] vs. ± % [n = 11]; p < .05). In addition, lung elastin was decreased by ~75% (p < .05) and hydroxyproline was decreased by ~50% (NS) in the 21- aminosteroid-treated group when compared with the bleomycin control group. At 7 and 14 days after bleomycin exposure, all bleomycin-exposed animals had evidence of increased lipid peroxidation (conjugated dienes and thiobarbituric acid-reactive substances), but the 21-aminosteroid-treated, bleomycin-exposed animals had significantly decreased evidence of lipid peroxidation when compared with bleomycin controls. Conclusions: The 21- aminosteroid can substantially protect animals from bleomycin-induced pulmonary fibrosis and may prove useful in other lung diseases where iron- dependent, free-radical reactions and/or lipid peroxidation are presumed mechanisms of toxicity.