EFFECTS OF INFLAMMATORY AGENTS ON ENDOTHELIAL LYSOSOMAL FRAGILITY AND THEIR INHIBITION BY ANTIINFLAMMATORY DRUGS

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Abstract
Endothelial cells from human unbilical veins were maintained in tissue culture. The fragility of lysosomal membranes were studied by microdensitometry. Histamine (50 μm to 10 mm), 4‐methylhistamine (100 nm to 10 mm) and dimaprit (100 nm to 10 mm) increased lysosomal fragility. 2‐Thiazolyethylamine and 2‐pyridylethylamine (100 nm to 10 mm) had no effect. Prostaglandins E1 and E2 (3 nm to 30 μm) and prostaglandin F2α (2 nm to 20 μm) had no direct effect. Low concentrations of prostaglandins E1 and E2 inhibited the fragility induced by histamine 100 μm. Bradykinin (100 nm to 100 μm) decreased fragility. The increase in fragility induced by histamine 100 μm or dimaprit 100 μm was inhibited by cimetidine (100 μm and 1 mm) but not by mepyramine (1 μm to 1 mm). Pretreatment with indomethacin, hydrocortisone, ibuprofen and sodium salicylate caused a dose‐dependent inhibition of histamine‐induced fragility. Threshold concentrations were 1 pm, 100 pm, 10 nm and 10 μm, respectively. Lignocaine (1 μm to 1 mm) had no direct effect and did not decrease histamine‐induced fragility.