IBUPROFEN INHIBITS RAT-BRAIN DEAMIDATION OF ANANDAMIDE AT PHARMACOLOGICALLY RELEVANT CONCENTRATIONS - MODE OF INHIBITION AND STRUCTURE-ACTIVITY RELATIONSHIP

The ability of rat brain (minus cerebellum) homogenates to deamidate a rachidonyl ethanolamide (anandamide) was determined with a custom-synt hesized substrate, arachidonyl ethanolamide-[1-H-3] ([(3)Hlanandamide) . Conditions whereby initial velocities were measured were established . The homogenates deamidated anandamide with a K-m value of 0.8 (mu M and a V-max value of 1.73 nmol . (mg protein)(-1) . min(-1). The deami dation of 2 mu(M) [H-3]anandamide was inhibited by phenylmethylsulfony l fluoride and arachidonyl trifluoromethyl ketone with IC50 values of 3.7 and 0.23 mu M, respectively. Ibuprofen inhibited anandamide deamid ation in a mixed fashion, with K-i and K'(i) values of 82 and 1420 mu M. At an anandamide concentration of 2 mu M, the IC50 values (in mu M) of a series of compounds related in structure to ibuprofen were as fo llows: suprofen, 170; ibuprofen, 270; fenoprofen, 480; naproxen, 550; ketoprofen, 650; diclofenac, similar to 1000. Sulindac produced 27% in hibition at a concentration of 1000 mu M, whereas isobutyric acid, hyd rocinnamic acid, acetylsalicylic acid and acetaminophen were essential ly inactive at concentrations less than or equal to 1 mM. We conclude that ibuprofen inhibits anandamide deamidation at pharmacologically re levant concentrations and that there is some specificity to the inhibi tion produced by ibuprofen and suprofen.