Prostaglandin synthesis by microsomes of circular and longitudinal gastrointestinal muscles

Experiments were performed to determine whether longitudinal and circular muscles from various regions of stomach and small bowel had the capacity to convert arachidonic acid (AA) to prostaglandins (PGs). PG production by the microsomal fractions of isolated muscles was assayed by determining the conversion of [14C]AA to 14C-labeled 6-keto-PGF1 alpha, PGF2 alpha, PGE2, PGD2, PGA2, and thromboxane B2. Individual PGs were identified by thin-layer chromatography. The metabolism of [14C]AA to [14C]PGs was linearly related to substrate concentration, enzyme concentration, and incubation time at 37 degrees C and was inhibited in a dose-dependent manner by indomethacin. Longitudinal and circular muscles from all tested regions (corpus, fundus, antrum, pylorus, duodenum, jejunum, and ileum) synthesized PGs. In all regions the major end products of AA metabolism were 6-keto-PGF1 alpha, PGE2, and PGF2 alpha. The data indicate that circular and longitudinal muscles from all regions of the stomach and small bowel contain the enzymatic apparatus necessary to convert AA into prostaglandins.