Prostaglandin biosynthesis in gastroduodenal mucosa: methodological difficulties and their implications.

A deficiency of locally synthesized prostaglandins has been suggested to underly gastric and duodenal ulcer disease and to mediate the mucosal lesions induced by non-steroidal anti-inflammatory drugs. The exact definition of their role is hampered by various methodological problems. First, the mucosal content of prostaglandins is affected by mechanical manipulation and homogenization and does not correspond to the rate of synthesis. Secondly, the assay of this rate in mass terms is also susceptible to these artefacts, and a steady state of prostaglandin secretion in vitro is usually not achieved. Thirdly, if prostaglandin synthesis is measured in vitro by the incorporation of labelled arachidonic acid, the possibly rate-limiting role of substrate supply is not taken into account. Thus, it is likely that a part of the disagreement in the field stems from the problems in measuring the true rates of prostaglandin synthesis in vivo.