Influence of prostaglandins on bovine abomasum: biosynthesis and in vitro motility experiments.

Pieces of the fundus, antrum pyloricum and pyloric sphincter of abomasa from freshly killed cows were studied for their capacity to biotransform arachidonic acid (AA) and for the effects of PG's on their in vitro motility. Biotransformation experiments revealed an AA-conversion (3.8 to 11.5%) into cyclooxygenase and lipoxygenase metabolites. The mucosa mainly synthetized hydroxy-eicosatetraenoic acids (HETE's) and PGE2 + TXB2. For the muscularis PGI2 was the major AA-metabolite. Incubation in the presence of indomethacin resulted in a reduction of the AA-conversion into cyclooxygenase metabolites. In the fundic strips the three PG's induced an increase in tension. In the antral strips PGF2 alpha and PGE2 resulted in an activation of spontaneous motility whereas PGI2 provoked a dose-dependent inhibition. The three PG's induced an inhibitory response in the tissue strips from the pyloric sphincter. The results suggest a possible function for PG's in the control of tone and motility of the bovine abomasum.