[Radioimmunoassay of prostaglandins (author's transl)]

Prostaglandins (PGs) can be measured by bioassay or combined gas-chromatography/mass spectrometry or by radioimmunoassay. The main advantage of the latter method is its great sensitivity. On the other hand, difficulties, with this method can arise from the small molecular weight of PGs and the large number of structurally closely related PGs and PG metabolites which cross-react in the various radioimmunoassays thus influencing the specificity of the method. Exogenous PGs exert a variety of effects on the gastro-intestinal tract. The effects on the various organs differ between the PGs tested and are species-dependent. Endogenous PGs have been found both in human and animal tissues of the gastrointestinal tract. PGE2 and its 15-keto-13, 14-dihydro-metabolite are the main PGs found in human gastric juice, while much smaller concentrations of PGF2alpha and PGA2 and their metabolites were detected. In human gastric mucosa both PG synthetase and PG-metabolizing enzymes were found to occur. Both enzyme systems can be influenced specifically by drugs. Inhibition of PG synthetase seems to correlate with gastric mucosal irritation, while inhibition of enzymatic PG inactivation might be associated with protection of gastro-intestinal mucosa. Results from animal experiments as well as clinical observations on humans indicate, that endogenous PGs might be involved in such syndromes as diarrhea, colitis, gastritis, tumors, acute pancreatitis and gastric ulcers caused by nonsteroidal anti-inflammatory drugs. The exact role, however, played by PGs in physiology and pathophysiology of the gastro-intestinal tract, awaits further investigations.