The effect of corticosteroid therapy on lysosomal enzymes and protein and lipid metabolism in rabbit lung after administration of Freund's adjuvant
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The effect of corticosteroid therapy on the bronchoalveolar cell response, the changes in activity of some lysosomal enzymes and the protein and lipid biosynthesis rates in lung tissue of normal rabbits and of rabbits after induction of an acute inflammation by the intravenous injection of complete Freund's adjuvant (CFA) 0.2 mlkg body weight was investigated. Three intramuscular injections of methylprednisolone acetate (Depo-Medrol) 1.2 mg/kg over a period of 8 days reduced the mean total bronchoalveolar free cell yields significantly. The percentages of lymphocytes and granulocytes were decreased. The increase in the macrophage percentage was associated with a significant increase in the acid phosphatase activity of the broncho-alveolar cells. The β-glucuronidase activity, on the other hand, was lowered in alveolar cells and even significantly suppressed in lung tissue. Protein and lipid biosynthesis was significantly retarded in lung tissue 8 days after the start of therapy. Administration of a single dose of CFA 0.2 ml/kg evoked an acute lung inflammation and a significant increase in total alveolar free cell yields. The macrophage percentage was reduced and the lymphocyte numbers doubled, whereas the granulocyte percentage increased more than sevenfold. The change in the percentage distribution of granulocytes may be associated with the marked increase in β-glucuronidase activity of the cells as well as of the lung tissue. In the inflammatory phase, protein biosynthesis was significantly increased but lipid synthesis was not affected. Corticosteroid therapy in animals treated with adjuvant reversed all the effects of CFA. It has very pronounced anti-inflammatory action and a catabolic effect on protein and lipid metabolism.
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