Release of platelet-activating factor (PAF) from human colon mucosa and its inhibition by 5-aminosalicylic acid.

Tissues from 6 operation specimens were incubated at 37 degrees C for 30 min +/- ricinoleic acid 6.25-100 micrograms/ml. PAF was determined in the incubates by scintillation proximity assay (Amersham) after extraction and purification. No PAF was detected in control samples (less than 0.4 ng/g/30 min), whereas ricinoleic acid 12.5-100 micrograms/ml stimulated PAF output (18.3 +/- 2.1 ng/g/30 min, mean +/- sem). 5-ASA 25-100 micrograms/ml caused a 5-100% inhibition of the PAF release by 50 micrograms/ml ricinoleic acid. The authors conclude that PAF can be released by damage to human colonic mucosa/submucosa, and that the inhibition of PAF release in ulcerative colitis may at least partly explain the therapeutic effect of 5-ASA.