Thiyl radicals in biosystems: inhibition of the prostaglandin metabolism by the cis-trans-isomerization of arachidonic acid double bonds.

This paper describes parallel and comparative experiments on the enzymatic cyclooxygenase (COX) driven conversion of arachidonic acid (AA, all-cis-5,8,11,14-eicosatetraenoic acid) into prostaglandins by using pure arachidonic acid and AA samples containing relatively small amounts of thiyl radical induced trans-isomers. The experiments were performed in a liquid aqueous model system using COX-1 as well as by the in vitro feeding of VD(3)-differentiated and LPS-stimulated promyelocytic HL-60 cells using the cell's own COX-2. In the model solution, all the different test methods used (oxygen consumption, ROS induced luminescence, and TMPD oxidation) indicated the greatly disproportionate, non-stoichiometric inhibition of the prostaglandin metabolism by the trans-isomers.