EXISTENCE OF AN ENZYMATIC PATHWAY FURNISHING ARACHIDONIC-ACID FOR PROSTAGLANDIN SYNTHESIS FROM ARACHIDONOYL COA IN RABBIT KIDNEY MEDULLA

We examined whether arachidonoyl CoA (AA-CoA) can be a possible suppli er of arachidonic acid (AA) for prostaglandin (PG) synthesis in rabbit kidney medulla. AA-CoA was preincubated with or without the 105000 g supernatant (cytosol) fraction from the kidney medulla for 5 min at 37 degrees C followed by the incubation with the microsomal fraction (0. 5 mg protein) (a rich source of PG synthesizing enzymes) in the presen ce of reduced glutathione and hydroquinone for 5 min at 37 degrees C, and the formed PGE(2), F-2 alpha and D-2 were measured by high-pressur e liquid chromatography using 9-anthryldiazomethane for derivatization . The addition of AA-CoA (20 nmol) alone changed the total PG formatio n (the sum of PGE(2), F-2 alpha and D-2) from 0.14 to 1.55 ng. When th e cytosolic fraction (10-100 mu l) was added together with 20 nmol-AA- CoA in the preincubation mixture, total PG formation was further incre ased 2- to 3-fold compared to AA-CoA alone. Experiments utilizing AA, instead of AA-CoA and boiled cytosolic fraction revealed that the stim ulatory action of the cytosolic fraction on the AA-CoA-induced PG synt hesis may not be due to the effect on cyclooxygenase activity and due to long-chain acyl CoA hydrolase. These results show that long-chain a cyl CoA hydrolase which hydrolyzes AA-CoA to AA is present in the cyto sol of rabbit kidney medulla and suggest that this enzyme activity is a potential mediator of supply of AA for PG synthesis in this region. (C) 1994 Academic Press, Inc.