MEASUREMENT OF PROSTAGLANDIN E(2) IN RECTAL MUCOSA IN HUMAN-SUBJECTS - A METHOD STUDY

It has been demonstrated and confirmed that certain nonsteroidal anti- inflammatory drugs which inhibit cyclooxygenase and the synthesis of p rostaglandins and other eicosanoids, can reduce the formation of both colon polyps and cancers in experimental animals given known carcinoge ns. Additionally, the results of several epidemiologic studies have su ggested that nonsteroidal anti-inflammatory drugs may reduce the risk of colon polyp occurrence and/or colon cancer mortality. We have carri ed out a study to evaluate the methodology of the measurement of prost aglandin E(2) (PGE(2)) in human colonic mucosa because its concentrati on may serve as a valuable intermediate marker of the pharmacological activity in Phase II studies of nonsteroidal antiinflammatory drugs as colon cancer preventive agents. We studied all aspects of the actual measurement of PGE(2) including the extraction efficiency of the PCE(2 ) from the mucosa, the precision of the assay and calculation of the P GE(2) content in terms of milligrams of protein in the sample, the inh ibition of PCE(2) by indomethacin over time, the reproducibility of th e measurement within one homogenate, the rate of PCE(2) production ove r time, the effect of adding indomethacin versus snap freezing on PGE( 2) production, the stability of PCE(2) in tissues over time stored in liquid nitrogen, and the variability of the measurement of PGE(2) in s eparate biopsies from one individual. Our studies indicated that the m ost reliable method for accurate and consistent measurements of PGE(2) was to add the mucosal tissue instantly after biopsy to an indomethac in buffer that effectively inhibited the in vitro formation of PCE(2).