The effect of prostaglandin E on the vascular permeability and the prostaglandin synthesizing and metabolizing activities in rat carrageenin granuloma were studied. Radioiodinated human serum albumin was used as an indicator for the measurement of vascular permeability. The dose necessary to induce significant increase of vascular permeability in the inflammatory tissue was found at least in the order of 0.5 μg for PGE1 and 5 μg for PGE2. The prostaglandin synthesizing system was characterised by a radiometric assay. Two main products (PI and PII) were formed from [1-14C]arachidonic acid, while PGE2 and PGF2α were hardly formed. The prostaglandin metabolizing activity was measured by a reversed-phase partition chromatography technique. Both of the granuloma exudate and granuloma pouch wall were found to have little enzymatic activity for metabolizing PGE2. The results strongly suggest that contribution of endogenous PGE as a mediator of vascular permeability response in the granulomatous inflammation is minor at best.
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